diff --git a/eth2/state_processing/src/common/get_attesting_indices.rs b/eth2/state_processing/src/common/get_attesting_indices.rs
index a45eeb881..c627c366b 100644
--- a/eth2/state_processing/src/common/get_attesting_indices.rs
+++ b/eth2/state_processing/src/common/get_attesting_indices.rs
@@ -3,7 +3,7 @@ use types::*;
 
 /// Returns validator indices which participated in the attestation, sorted by increasing index.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn get_attesting_indices<T: EthSpec>(
     state: &BeaconState<T>,
     attestation_data: &AttestationData,
@@ -18,7 +18,7 @@ pub fn get_attesting_indices<T: EthSpec>(
 
 /// Returns validator indices which participated in the attestation, unsorted.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn get_attesting_indices_unsorted<T: EthSpec>(
     state: &BeaconState<T>,
     attestation_data: &AttestationData,
diff --git a/eth2/state_processing/src/common/initiate_validator_exit.rs b/eth2/state_processing/src/common/initiate_validator_exit.rs
index 996dcdb2a..40b3d80fa 100644
--- a/eth2/state_processing/src/common/initiate_validator_exit.rs
+++ b/eth2/state_processing/src/common/initiate_validator_exit.rs
@@ -3,7 +3,7 @@ use types::{BeaconStateError as Error, *};
 
 /// Initiate the exit of the validator of the given `index`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn initiate_validator_exit<T: EthSpec>(
     state: &mut BeaconState<T>,
     index: usize,
diff --git a/eth2/state_processing/src/common/slash_validator.rs b/eth2/state_processing/src/common/slash_validator.rs
index 2a2db1a77..0908f4a39 100644
--- a/eth2/state_processing/src/common/slash_validator.rs
+++ b/eth2/state_processing/src/common/slash_validator.rs
@@ -3,7 +3,7 @@ use types::{BeaconStateError as Error, *};
 
 /// Slash the validator with index ``index``.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn slash_validator<T: EthSpec>(
     state: &mut BeaconState<T>,
     slashed_index: usize,
diff --git a/eth2/state_processing/src/common/verify_bitfield.rs b/eth2/state_processing/src/common/verify_bitfield.rs
index 886269a54..0d4045c2e 100644
--- a/eth2/state_processing/src/common/verify_bitfield.rs
+++ b/eth2/state_processing/src/common/verify_bitfield.rs
@@ -4,7 +4,7 @@ use types::*;
 ///
 /// Is title `verify_bitfield` in spec.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_bitfield_length(bitfield: &Bitfield, committee_size: usize) -> bool {
     if bitfield.num_bytes() != ((committee_size + 7) / 8) {
         return false;
diff --git a/eth2/state_processing/src/get_genesis_state.rs b/eth2/state_processing/src/get_genesis_state.rs
index 18a1e7c35..5cb8648ee 100644
--- a/eth2/state_processing/src/get_genesis_state.rs
+++ b/eth2/state_processing/src/get_genesis_state.rs
@@ -9,7 +9,7 @@ pub enum GenesisError {
 
 /// Returns the genesis `BeaconState`
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn get_genesis_beacon_state<T: EthSpec>(
     genesis_validator_deposits: &[Deposit],
     genesis_time: u64,
diff --git a/eth2/state_processing/src/per_block_processing.rs b/eth2/state_processing/src/per_block_processing.rs
index c65c6d17b..ab7e5a320 100644
--- a/eth2/state_processing/src/per_block_processing.rs
+++ b/eth2/state_processing/src/per_block_processing.rs
@@ -40,7 +40,7 @@ mod verify_transfer;
 /// Returns `Ok(())` if the block is valid and the state was successfully updated. Otherwise
 /// returns an error describing why the block was invalid or how the function failed to execute.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn per_block_processing<T: EthSpec>(
     state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -55,7 +55,7 @@ pub fn per_block_processing<T: EthSpec>(
 /// Returns `Ok(())` if the block is valid and the state was successfully updated. Otherwise
 /// returns an error describing why the block was invalid or how the function failed to execute.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn per_block_processing_without_verifying_block_signature<T: EthSpec>(
     state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -70,7 +70,7 @@ pub fn per_block_processing_without_verifying_block_signature<T: EthSpec>(
 /// Returns `Ok(())` if the block is valid and the state was successfully updated. Otherwise
 /// returns an error describing why the block was invalid or how the function failed to execute.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn per_block_processing_signature_optional<T: EthSpec>(
     mut state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -97,7 +97,7 @@ fn per_block_processing_signature_optional<T: EthSpec>(
 
 /// Processes the block header.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_block_header<T: EthSpec>(
     state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -132,7 +132,7 @@ pub fn process_block_header<T: EthSpec>(
 
 /// Verifies the signature of a block.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_block_signature<T: EthSpec>(
     state: &BeaconState<T>,
     block: &BeaconBlock,
@@ -160,7 +160,7 @@ pub fn verify_block_signature<T: EthSpec>(
 /// Verifies the `randao_reveal` against the block's proposer pubkey and updates
 /// `state.latest_randao_mixes`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_randao<T: EthSpec>(
     state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -191,7 +191,7 @@ pub fn process_randao<T: EthSpec>(
 
 /// Update the `state.eth1_data_votes` based upon the `eth1_data` provided.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_eth1_data<T: EthSpec>(
     state: &mut BeaconState<T>,
     eth1_data: &Eth1Data,
@@ -217,7 +217,7 @@ pub fn process_eth1_data<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_proposer_slashings<T: EthSpec>(
     state: &mut BeaconState<T>,
     proposer_slashings: &[ProposerSlashing],
@@ -250,7 +250,7 @@ pub fn process_proposer_slashings<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_attester_slashings<T: EthSpec>(
     state: &mut BeaconState<T>,
     attester_slashings: &[AttesterSlashing],
@@ -308,7 +308,7 @@ pub fn process_attester_slashings<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_attestations<T: EthSpec>(
     state: &mut BeaconState<T>,
     attestations: &[Attestation],
@@ -357,7 +357,7 @@ pub fn process_attestations<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_deposits<T: EthSpec>(
     state: &mut BeaconState<T>,
     deposits: &[Deposit],
@@ -434,7 +434,7 @@ pub fn process_deposits<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_exits<T: EthSpec>(
     state: &mut BeaconState<T>,
     voluntary_exits: &[VoluntaryExit],
@@ -466,7 +466,7 @@ pub fn process_exits<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_transfers<T: EthSpec>(
     state: &mut BeaconState<T>,
     transfers: &[Transfer],
diff --git a/eth2/state_processing/src/per_block_processing/validate_attestation.rs b/eth2/state_processing/src/per_block_processing/validate_attestation.rs
index 379b921f4..a2ee268bb 100644
--- a/eth2/state_processing/src/per_block_processing/validate_attestation.rs
+++ b/eth2/state_processing/src/per_block_processing/validate_attestation.rs
@@ -11,7 +11,7 @@ use types::*;
 ///
 /// Returns `Ok(())` if the `Attestation` is valid, otherwise indicates the reason for invalidity.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn validate_attestation<T: EthSpec>(
     state: &BeaconState<T>,
     attestation: &Attestation,
@@ -34,7 +34,7 @@ pub fn validate_attestation_time_independent_only<T: EthSpec>(
 ///
 /// Returns `Ok(())` if the `Attestation` is valid, otherwise indicates the reason for invalidity.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn validate_attestation_without_signature<T: EthSpec>(
     state: &BeaconState<T>,
     attestation: &Attestation,
@@ -47,7 +47,7 @@ pub fn validate_attestation_without_signature<T: EthSpec>(
 /// given state, optionally validating the aggregate signature.
 ///
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn validate_attestation_parametric<T: EthSpec>(
     state: &BeaconState<T>,
     attestation: &Attestation,
@@ -99,7 +99,7 @@ fn validate_attestation_parametric<T: EthSpec>(
 
 /// Check target epoch, source epoch, source root, and source crosslink.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn verify_casper_ffg_vote<T: EthSpec>(
     attestation: &Attestation,
     state: &BeaconState<T>,
diff --git a/eth2/state_processing/src/per_block_processing/verify_attester_slashing.rs b/eth2/state_processing/src/per_block_processing/verify_attester_slashing.rs
index 7e1fa5e66..3ae32d72a 100644
--- a/eth2/state_processing/src/per_block_processing/verify_attester_slashing.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_attester_slashing.rs
@@ -8,7 +8,7 @@ use types::*;
 ///
 /// Returns `Ok(())` if the `AttesterSlashing` is valid, otherwise indicates the reason for invalidity.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_attester_slashing<T: EthSpec>(
     state: &BeaconState<T>,
     attester_slashing: &AttesterSlashing,
@@ -39,7 +39,7 @@ pub fn verify_attester_slashing<T: EthSpec>(
 ///
 /// Returns Ok(indices) if `indices.len() > 0`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn get_slashable_indices<T: EthSpec>(
     state: &BeaconState<T>,
     attester_slashing: &AttesterSlashing,
diff --git a/eth2/state_processing/src/per_block_processing/verify_deposit.rs b/eth2/state_processing/src/per_block_processing/verify_deposit.rs
index da2353bb9..860e9cd26 100644
--- a/eth2/state_processing/src/per_block_processing/verify_deposit.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_deposit.rs
@@ -5,7 +5,7 @@ use types::*;
 
 /// Verify `Deposit.pubkey` signed `Deposit.signature`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_deposit_signature<T: EthSpec>(
     state: &BeaconState<T>,
     deposit: &Deposit,
@@ -25,7 +25,7 @@ pub fn verify_deposit_signature<T: EthSpec>(
 
 /// Verify that the `Deposit` index is correct.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_deposit_index<T: EthSpec>(
     state: &BeaconState<T>,
     deposit: &Deposit,
@@ -57,7 +57,7 @@ pub fn get_existing_validator_index<T: EthSpec>(
 
 /// Verify that a deposit is included in the state's eth1 deposit root.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_deposit_merkle_proof<T: EthSpec>(
     state: &BeaconState<T>,
     deposit: &Deposit,
diff --git a/eth2/state_processing/src/per_block_processing/verify_exit.rs b/eth2/state_processing/src/per_block_processing/verify_exit.rs
index 2a3a29b3f..4bfad5f19 100644
--- a/eth2/state_processing/src/per_block_processing/verify_exit.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_exit.rs
@@ -7,7 +7,7 @@ use types::*;
 ///
 /// Returns `Ok(())` if the `Exit` is valid, otherwise indicates the reason for invalidity.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_exit<T: EthSpec>(
     state: &BeaconState<T>,
     exit: &VoluntaryExit,
@@ -18,7 +18,7 @@ pub fn verify_exit<T: EthSpec>(
 
 /// Like `verify_exit` but doesn't run checks which may become true in future states.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_exit_time_independent_only<T: EthSpec>(
     state: &BeaconState<T>,
     exit: &VoluntaryExit,
@@ -29,7 +29,7 @@ pub fn verify_exit_time_independent_only<T: EthSpec>(
 
 /// Parametric version of `verify_exit` that skips some checks if `time_independent_only` is true.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn verify_exit_parametric<T: EthSpec>(
     state: &BeaconState<T>,
     exit: &VoluntaryExit,
diff --git a/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs b/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs
index f06f1e900..4597082df 100644
--- a/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_indexed_attestation.rs
@@ -8,7 +8,7 @@ use types::*;
 
 /// Verify an `IndexedAttestation`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_indexed_attestation<T: EthSpec>(
     state: &BeaconState<T>,
     indexed_attestation: &IndexedAttestation,
@@ -19,7 +19,7 @@ pub fn verify_indexed_attestation<T: EthSpec>(
 
 /// Verify but don't check the signature.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_indexed_attestation_without_signature<T: EthSpec>(
     state: &BeaconState<T>,
     indexed_attestation: &IndexedAttestation,
@@ -30,7 +30,7 @@ pub fn verify_indexed_attestation_without_signature<T: EthSpec>(
 
 /// Optionally check the signature.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn verify_indexed_attestation_parametric<T: EthSpec>(
     state: &BeaconState<T>,
     indexed_attestation: &IndexedAttestation,
@@ -107,7 +107,7 @@ where
 
 /// Verify the signature of an IndexedAttestation.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn verify_indexed_attestation_signature<T: EthSpec>(
     state: &BeaconState<T>,
     indexed_attestation: &IndexedAttestation,
diff --git a/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs b/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs
index 744427ad9..b2419a05b 100644
--- a/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs
@@ -7,7 +7,7 @@ use types::*;
 ///
 /// Returns `Ok(())` if the `ProposerSlashing` is valid, otherwise indicates the reason for invalidity.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_proposer_slashing<T: EthSpec>(
     proposer_slashing: &ProposerSlashing,
     state: &BeaconState<T>,
@@ -65,7 +65,7 @@ pub fn verify_proposer_slashing<T: EthSpec>(
 ///
 /// Returns `true` if the signature is valid.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn verify_header_signature<T: EthSpec>(
     header: &BeaconBlockHeader,
     pubkey: &PublicKey,
diff --git a/eth2/state_processing/src/per_block_processing/verify_transfer.rs b/eth2/state_processing/src/per_block_processing/verify_transfer.rs
index de4cef44f..e99ed6a9a 100644
--- a/eth2/state_processing/src/per_block_processing/verify_transfer.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_transfer.rs
@@ -8,7 +8,7 @@ use types::*;
 ///
 /// Returns `Ok(())` if the `Transfer` is valid, otherwise indicates the reason for invalidity.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_transfer<T: EthSpec>(
     state: &BeaconState<T>,
     transfer: &Transfer,
@@ -19,7 +19,7 @@ pub fn verify_transfer<T: EthSpec>(
 
 /// Like `verify_transfer` but doesn't run checks which may become true in future states.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn verify_transfer_time_independent_only<T: EthSpec>(
     state: &BeaconState<T>,
     transfer: &Transfer,
@@ -37,7 +37,7 @@ pub fn verify_transfer_time_independent_only<T: EthSpec>(
 ///     present or future.
 /// - Validator transfer eligibility (e.g., is withdrawable)
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn verify_transfer_parametric<T: EthSpec>(
     state: &BeaconState<T>,
     transfer: &Transfer,
@@ -154,7 +154,7 @@ fn verify_transfer_parametric<T: EthSpec>(
 ///
 /// Does not check that the transfer is valid, however checks for overflow in all actions.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn execute_transfer<T: EthSpec>(
     state: &mut BeaconState<T>,
     transfer: &Transfer,
diff --git a/eth2/state_processing/src/per_epoch_processing.rs b/eth2/state_processing/src/per_epoch_processing.rs
index 05ef7f658..26091d49e 100644
--- a/eth2/state_processing/src/per_epoch_processing.rs
+++ b/eth2/state_processing/src/per_epoch_processing.rs
@@ -26,7 +26,7 @@ pub type WinningRootHashSet = HashMap<u64, WinningRoot>;
 /// Mutates the given `BeaconState`, returning early if an error is encountered. If an error is
 /// returned, a state might be "half-processed" and therefore in an invalid state.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn per_epoch_processing<T: EthSpec>(
     state: &mut BeaconState<T>,
     spec: &ChainSpec,
@@ -80,7 +80,7 @@ pub fn per_epoch_processing<T: EthSpec>(
 /// - `finalized_epoch`
 /// - `finalized_root`
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_justification_and_finalization<T: EthSpec>(
     state: &mut BeaconState<T>,
     total_balances: &TotalBalances,
@@ -147,7 +147,7 @@ pub fn process_justification_and_finalization<T: EthSpec>(
 ///
 /// Also returns a `WinningRootHashSet` for later use during epoch processing.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_crosslinks<T: EthSpec>(
     state: &mut BeaconState<T>,
     spec: &ChainSpec,
@@ -183,7 +183,7 @@ pub fn process_crosslinks<T: EthSpec>(
 
 /// Finish up an epoch update.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_final_updates<T: EthSpec>(
     state: &mut BeaconState<T>,
     spec: &ChainSpec,
diff --git a/eth2/state_processing/src/per_epoch_processing/apply_rewards.rs b/eth2/state_processing/src/per_epoch_processing/apply_rewards.rs
index 7ddba6f38..88b51aae8 100644
--- a/eth2/state_processing/src/per_epoch_processing/apply_rewards.rs
+++ b/eth2/state_processing/src/per_epoch_processing/apply_rewards.rs
@@ -32,7 +32,7 @@ impl std::ops::AddAssign for Delta {
 
 /// Apply attester and proposer rewards.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_rewards_and_penalties<T: EthSpec>(
     state: &mut BeaconState<T>,
     validator_statuses: &mut ValidatorStatuses,
@@ -74,7 +74,7 @@ pub fn process_rewards_and_penalties<T: EthSpec>(
 
 /// For each attesting validator, reward the proposer who was first to include their attestation.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn get_proposer_deltas<T: EthSpec>(
     deltas: &mut Vec<Delta>,
     state: &BeaconState<T>,
@@ -111,7 +111,7 @@ fn get_proposer_deltas<T: EthSpec>(
 
 /// Apply rewards for participation in attestations during the previous epoch.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn get_attestation_deltas<T: EthSpec>(
     deltas: &mut Vec<Delta>,
     state: &BeaconState<T>,
@@ -144,7 +144,7 @@ fn get_attestation_deltas<T: EthSpec>(
 
 /// Determine the delta for a single validator, sans proposer rewards.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn get_attestation_delta(
     validator: &ValidatorStatus,
     total_balances: &TotalBalances,
@@ -224,7 +224,7 @@ fn get_attestation_delta(
 
 /// Calculate the deltas based upon the winning roots for attestations during the previous epoch.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn get_crosslink_deltas<T: EthSpec>(
     deltas: &mut Vec<Delta>,
     state: &BeaconState<T>,
@@ -258,7 +258,7 @@ fn get_crosslink_deltas<T: EthSpec>(
 
 /// Returns the base reward for some validator.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn get_base_reward<T: EthSpec>(
     state: &BeaconState<T>,
     index: usize,
diff --git a/eth2/state_processing/src/per_epoch_processing/process_slashings.rs b/eth2/state_processing/src/per_epoch_processing/process_slashings.rs
index 020534f80..3213b3230 100644
--- a/eth2/state_processing/src/per_epoch_processing/process_slashings.rs
+++ b/eth2/state_processing/src/per_epoch_processing/process_slashings.rs
@@ -2,7 +2,7 @@ use types::{BeaconStateError as Error, *};
 
 /// Process slashings.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_slashings<T: EthSpec>(
     state: &mut BeaconState<T>,
     current_total_balance: u64,
diff --git a/eth2/state_processing/src/per_epoch_processing/registry_updates.rs b/eth2/state_processing/src/per_epoch_processing/registry_updates.rs
index 469a14fdd..f97841d72 100644
--- a/eth2/state_processing/src/per_epoch_processing/registry_updates.rs
+++ b/eth2/state_processing/src/per_epoch_processing/registry_updates.rs
@@ -5,7 +5,7 @@ use types::*;
 
 /// Peforms a validator registry update, if required.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn process_registry_updates<T: EthSpec>(
     state: &mut BeaconState<T>,
     spec: &ChainSpec,
diff --git a/eth2/state_processing/src/per_epoch_processing/validator_statuses.rs b/eth2/state_processing/src/per_epoch_processing/validator_statuses.rs
index 45ef3419b..ece9174ca 100644
--- a/eth2/state_processing/src/per_epoch_processing/validator_statuses.rs
+++ b/eth2/state_processing/src/per_epoch_processing/validator_statuses.rs
@@ -162,7 +162,7 @@ impl ValidatorStatuses {
     /// - Active validators
     /// - Total balances for the current and previous epochs.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn new<T: EthSpec>(
         state: &BeaconState<T>,
         spec: &ChainSpec,
@@ -202,7 +202,7 @@ impl ValidatorStatuses {
     /// Process some attestations from the given `state` updating the `statuses` and
     /// `total_balances` fields.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn process_attestations<T: EthSpec>(
         &mut self,
         state: &BeaconState<T>,
@@ -289,7 +289,7 @@ impl ValidatorStatuses {
     /// Update the `statuses` for each validator based upon whether or not they attested to the
     /// "winning" shard block root for the previous epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn process_winning_roots<T: EthSpec>(
         &mut self,
         state: &BeaconState<T>,
@@ -323,7 +323,7 @@ impl ValidatorStatuses {
 
 /// Returns `true` if some `PendingAttestation` is from the supplied `epoch`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn is_from_epoch(a: &PendingAttestation, epoch: Epoch) -> bool {
     a.data.target_epoch == epoch
 }
@@ -331,7 +331,7 @@ fn is_from_epoch(a: &PendingAttestation, epoch: Epoch) -> bool {
 /// Returns `true` if the attestation's FFG target is equal to the hash of the `state`'s first
 /// beacon block in the given `epoch`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn target_matches_epoch_start_block<T: EthSpec>(
     a: &PendingAttestation,
     state: &BeaconState<T>,
@@ -346,7 +346,7 @@ fn target_matches_epoch_start_block<T: EthSpec>(
 /// Returns `true` if a `PendingAttestation` and `BeaconState` share the same beacon block hash for
 /// the current slot of the `PendingAttestation`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn has_common_beacon_block_root<T: EthSpec>(
     a: &PendingAttestation,
     state: &BeaconState<T>,
diff --git a/eth2/state_processing/src/per_epoch_processing/winning_root.rs b/eth2/state_processing/src/per_epoch_processing/winning_root.rs
index 62917a134..ab4381a3c 100644
--- a/eth2/state_processing/src/per_epoch_processing/winning_root.rs
+++ b/eth2/state_processing/src/per_epoch_processing/winning_root.rs
@@ -16,7 +16,7 @@ impl WinningRoot {
     /// A winning root is "better" than another if it has a higher `total_attesting_balance`. Ties
     /// are broken by favouring the higher `crosslink_data_root` value.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn is_better_than(&self, other: &Self) -> bool {
         (
             self.total_attesting_balance,
@@ -34,7 +34,7 @@ impl WinningRoot {
 /// The `WinningRoot` object also contains additional fields that are useful in later stages of
 /// per-epoch processing.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn winning_root<T: EthSpec>(
     state: &BeaconState<T>,
     shard: u64,
diff --git a/eth2/state_processing/src/per_slot_processing.rs b/eth2/state_processing/src/per_slot_processing.rs
index 8adfe988b..6abd0a075 100644
--- a/eth2/state_processing/src/per_slot_processing.rs
+++ b/eth2/state_processing/src/per_slot_processing.rs
@@ -9,7 +9,7 @@ pub enum Error {
 
 /// Advances a state forward by one slot, performing per-epoch processing if required.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn per_slot_processing<T: EthSpec>(
     state: &mut BeaconState<T>,
     spec: &ChainSpec,
diff --git a/eth2/types/src/attestation.rs b/eth2/types/src/attestation.rs
index 682716073..40f97119d 100644
--- a/eth2/types/src/attestation.rs
+++ b/eth2/types/src/attestation.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// Details an attestation that can be slashable.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/attestation_data.rs b/eth2/types/src/attestation_data.rs
index 3b0f529d6..e3e989baa 100644
--- a/eth2/types/src/attestation_data.rs
+++ b/eth2/types/src/attestation_data.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// The data upon which an attestation is based.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/attestation_data_and_custody_bit.rs b/eth2/types/src/attestation_data_and_custody_bit.rs
index e2d949ae8..601bc4041 100644
--- a/eth2/types/src/attestation_data_and_custody_bit.rs
+++ b/eth2/types/src/attestation_data_and_custody_bit.rs
@@ -7,7 +7,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Used for pairing an attestation with a proof-of-custody.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/attester_slashing.rs b/eth2/types/src/attester_slashing.rs
index 2b6402fcc..85770d290 100644
--- a/eth2/types/src/attester_slashing.rs
+++ b/eth2/types/src/attester_slashing.rs
@@ -7,7 +7,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Two conflicting attestations.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/beacon_block.rs b/eth2/types/src/beacon_block.rs
index 2a829fda2..f823f234e 100644
--- a/eth2/types/src/beacon_block.rs
+++ b/eth2/types/src/beacon_block.rs
@@ -10,7 +10,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// A block of the `BeaconChain`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
@@ -36,7 +36,7 @@ pub struct BeaconBlock {
 impl BeaconBlock {
     /// Returns an empty block to be used during genesis.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn empty(spec: &ChainSpec) -> BeaconBlock {
         BeaconBlock {
             slot: spec.genesis_slot,
@@ -63,7 +63,7 @@ impl BeaconBlock {
 
     /// Returns the `tree_hash_root | update` of the block.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn canonical_root(&self) -> Hash256 {
         Hash256::from_slice(&self.tree_hash_root()[..])
     }
@@ -75,7 +75,7 @@ impl BeaconBlock {
     ///
     /// Note: performs a full tree-hash of `self.body`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn block_header(&self) -> BeaconBlockHeader {
         BeaconBlockHeader {
             slot: self.slot,
@@ -88,7 +88,7 @@ impl BeaconBlock {
 
     /// Returns a "temporary" header, where the `state_root` is `spec.zero_hash`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn temporary_block_header(&self, spec: &ChainSpec) -> BeaconBlockHeader {
         BeaconBlockHeader {
             state_root: spec.zero_hash,
diff --git a/eth2/types/src/beacon_block_body.rs b/eth2/types/src/beacon_block_body.rs
index e3609d889..6b0eb1401 100644
--- a/eth2/types/src/beacon_block_body.rs
+++ b/eth2/types/src/beacon_block_body.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// The body of a `BeaconChain` block, containing operations.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/beacon_block_header.rs b/eth2/types/src/beacon_block_header.rs
index f58803c20..829130222 100644
--- a/eth2/types/src/beacon_block_header.rs
+++ b/eth2/types/src/beacon_block_header.rs
@@ -10,7 +10,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// A header of a `BeaconBlock`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
@@ -36,14 +36,14 @@ pub struct BeaconBlockHeader {
 impl BeaconBlockHeader {
     /// Returns the `tree_hash_root` of the header.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn canonical_root(&self) -> Hash256 {
         Hash256::from_slice(&self.signed_root()[..])
     }
 
     /// Given a `body`, consumes `self` and returns a complete `BeaconBlock`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn into_block(self, body: BeaconBlockBody) -> BeaconBlock {
         BeaconBlock {
             slot: self.slot,
diff --git a/eth2/types/src/beacon_state.rs b/eth2/types/src/beacon_state.rs
index ba70b21d3..f76676a2b 100644
--- a/eth2/types/src/beacon_state.rs
+++ b/eth2/types/src/beacon_state.rs
@@ -63,7 +63,7 @@ pub enum Error {
 
 /// The state of the `BeaconChain` at some slot.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
@@ -157,7 +157,7 @@ impl<T: EthSpec> BeaconState<T> {
     /// This does not fully build a genesis beacon state, it omits processing of initial validator
     /// deposits. To obtain a full genesis beacon state, use the `BeaconStateBuilder`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn genesis(
         genesis_time: u64,
         latest_eth1_data: Eth1Data,
@@ -234,7 +234,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Returns the `tree_hash_root` of the state.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn canonical_root(&self) -> Hash256 {
         Hash256::from_slice(&self.tree_hash_root()[..])
     }
@@ -263,7 +263,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// The epoch corresponding to `self.slot`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn current_epoch(&self) -> Epoch {
         self.slot.epoch(T::slots_per_epoch())
     }
@@ -272,7 +272,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// If the current epoch is the genesis epoch, the genesis_epoch is returned.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn previous_epoch(&self) -> Epoch {
         let current_epoch = self.current_epoch();
         if current_epoch > T::genesis_epoch() {
@@ -284,7 +284,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// The epoch following `self.current_epoch()`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn next_epoch(&self) -> Epoch {
         self.current_epoch() + 1
     }
@@ -313,7 +313,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// Note: Utilizes the cache and will fail if the appropriate cache is not initialized.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_attestation_slot(&self, attestation_data: &AttestationData) -> Result<Slot, Error> {
         let target_relative_epoch =
             RelativeEpoch::from_epoch(self.current_epoch(), attestation_data.target_epoch)?;
@@ -342,7 +342,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// Does not utilize the cache, performs a full iteration over the validator registry.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn get_active_validator_indices(&self, epoch: Epoch) -> Vec<usize> {
         get_active_validator_indices(&self.validator_registry, epoch)
     }
@@ -362,7 +362,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// Note: Utilizes the cache and will fail if the appropriate cache is not initialized.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn get_crosslink_committees_at_slot(
         &self,
         slot: Slot,
@@ -379,7 +379,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// Note: Utilizes the cache and will fail if the appropriate cache is not initialized.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_crosslink_committee_for_shard(
         &self,
         shard: u64,
@@ -396,7 +396,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Returns the beacon proposer index for the `slot` in the given `relative_epoch`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     // NOTE: be sure to test this bad boy.
     pub fn get_beacon_proposer_index(
         &self,
@@ -433,7 +433,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Safely obtains the index for latest block roots, given some `slot`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     fn get_latest_block_roots_index(&self, slot: Slot) -> Result<usize, Error> {
         if (slot < self.slot) && (self.slot <= slot + self.latest_block_roots.len() as u64) {
             Ok(slot.as_usize() % self.latest_block_roots.len())
@@ -444,7 +444,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Return the block root at a recent `slot`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn get_block_root(&self, slot: Slot) -> Result<&Hash256, BeaconStateError> {
         let i = self.get_latest_block_roots_index(slot)?;
         Ok(&self.latest_block_roots[i])
@@ -452,7 +452,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Return the block root at a recent `epoch`.
     ///
-    /// Spec v0.6.0
+    /// Spec v0.6.3
     // NOTE: the spec calls this get_block_root
     pub fn get_block_root_at_epoch(&self, epoch: Epoch) -> Result<&Hash256, BeaconStateError> {
         self.get_block_root(epoch.start_slot(T::slots_per_epoch()))
@@ -460,7 +460,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Sets the block root for some given slot.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn set_block_root(
         &mut self,
         slot: Slot,
@@ -473,7 +473,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Safely obtains the index for `latest_randao_mixes`
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     fn get_randao_mix_index(&self, epoch: Epoch) -> Result<usize, Error> {
         let current_epoch = self.current_epoch();
         let len = T::LatestRandaoMixesLength::to_u64();
@@ -491,7 +491,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// See `Self::get_randao_mix`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn update_randao_mix(&mut self, epoch: Epoch, signature: &Signature) -> Result<(), Error> {
         let i = epoch.as_usize() % T::LatestRandaoMixesLength::to_usize();
 
@@ -504,7 +504,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Return the randao mix at a recent ``epoch``.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn get_randao_mix(&self, epoch: Epoch) -> Result<&Hash256, Error> {
         let i = self.get_randao_mix_index(epoch)?;
         Ok(&self.latest_randao_mixes[i])
@@ -512,7 +512,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Set the randao mix at a recent ``epoch``.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn set_randao_mix(&mut self, epoch: Epoch, mix: Hash256) -> Result<(), Error> {
         let i = self.get_randao_mix_index(epoch)?;
         self.latest_randao_mixes[i] = mix;
@@ -521,7 +521,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Safely obtains the index for `latest_active_index_roots`, given some `epoch`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn get_active_index_root_index(&self, epoch: Epoch, spec: &ChainSpec) -> Result<usize, Error> {
         let current_epoch = self.current_epoch();
 
@@ -537,7 +537,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Return the `active_index_root` at a recent `epoch`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_active_index_root(&self, epoch: Epoch, spec: &ChainSpec) -> Result<Hash256, Error> {
         let i = self.get_active_index_root_index(epoch, spec)?;
         Ok(self.latest_active_index_roots[i])
@@ -545,7 +545,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Set the `active_index_root` at a recent `epoch`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn set_active_index_root(
         &mut self,
         epoch: Epoch,
@@ -559,7 +559,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Replace `active_index_roots` with clones of `index_root`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn fill_active_index_roots_with(&mut self, index_root: Hash256) {
         self.latest_active_index_roots =
             vec![index_root; self.latest_active_index_roots.len()].into()
@@ -567,7 +567,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Safely obtains the index for latest state roots, given some `slot`.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     fn get_latest_state_roots_index(&self, slot: Slot) -> Result<usize, Error> {
         if (slot < self.slot) && (self.slot <= slot + self.latest_state_roots.len() as u64) {
             Ok(slot.as_usize() % self.latest_state_roots.len())
@@ -578,7 +578,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Gets the state root for some slot.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn get_state_root(&mut self, slot: Slot) -> Result<&Hash256, Error> {
         let i = self.get_latest_state_roots_index(slot)?;
         Ok(&self.latest_state_roots[i])
@@ -586,7 +586,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Sets the latest state root for slot.
     ///
-    /// Spec v0.5.1
+    /// Spec v0.6.3
     pub fn set_state_root(&mut self, slot: Slot, state_root: Hash256) -> Result<(), Error> {
         let i = self.get_latest_state_roots_index(slot)?;
         self.latest_state_roots[i] = state_root;
@@ -595,7 +595,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Safely obtains the index for `latest_slashed_balances`, given some `epoch`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn get_slashed_balance_index(&self, epoch: Epoch) -> Result<usize, Error> {
         let i = epoch.as_usize() % self.latest_slashed_balances.len();
 
@@ -610,7 +610,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Gets the total slashed balances for some epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_slashed_balance(&self, epoch: Epoch) -> Result<u64, Error> {
         let i = self.get_slashed_balance_index(epoch)?;
         Ok(self.latest_slashed_balances[i])
@@ -618,7 +618,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Sets the total slashed balances for some epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn set_slashed_balance(&mut self, epoch: Epoch, balance: u64) -> Result<(), Error> {
         let i = self.get_slashed_balance_index(epoch)?;
         self.latest_slashed_balances[i] = balance;
@@ -627,7 +627,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Get the attestations from the current or previous epoch.
     ///
-    /// Spec v0.6.0
+    /// Spec v0.6.3
     pub fn get_matching_source_attestations(
         &self,
         epoch: Epoch,
@@ -643,7 +643,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Get the current crosslink for a shard.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_current_crosslink(&self, shard: u64) -> Result<&Crosslink, Error> {
         self.current_crosslinks
             .get(shard as usize)
@@ -652,7 +652,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Get the previous crosslink for a shard.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_previous_crosslink(&self, shard: u64) -> Result<&Crosslink, Error> {
         self.previous_crosslinks
             .get(shard as usize)
@@ -661,7 +661,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Transform an attestation into the crosslink that it reinforces.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_crosslink_from_attestation_data(
         &self,
         data: &AttestationData,
@@ -680,7 +680,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Generate a seed for the given `epoch`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn generate_seed(&self, epoch: Epoch, spec: &ChainSpec) -> Result<Hash256, Error> {
         // Bypass the safe getter for RANDAO so we can gracefully handle the scenario where `epoch
         // == 0`.
@@ -701,7 +701,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Return the effective balance (also known as "balance at stake") for a validator with the given ``index``.
     ///
-    /// Spec v0.6.0
+    /// Spec v0.6.3
     pub fn get_effective_balance(
         &self,
         validator_index: usize,
@@ -715,7 +715,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     ///  Return the epoch at which an activation or exit triggered in ``epoch`` takes effect.
     ///
-    ///  Spec v0.5.1
+    ///  Spec v0.6.3
     pub fn get_delayed_activation_exit_epoch(&self, epoch: Epoch, spec: &ChainSpec) -> Epoch {
         epoch + 1 + spec.activation_exit_delay
     }
@@ -724,7 +724,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// Uses the epoch cache, and will error if it isn't initialized.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_churn_limit(&self, spec: &ChainSpec) -> Result<u64, Error> {
         Ok(std::cmp::max(
             spec.min_per_epoch_churn_limit,
@@ -738,7 +738,7 @@ impl<T: EthSpec> BeaconState<T> {
     ///
     /// Note: Utilizes the cache and will fail if the appropriate cache is not initialized.
     ///
-    /// Spec v0.6.2
+    /// Spec v0.6.3
     pub fn get_attestation_duties(
         &self,
         validator_index: usize,
@@ -751,7 +751,7 @@ impl<T: EthSpec> BeaconState<T> {
 
     /// Return the combined effective balance of an array of validators.
     ///
-    /// Spec v0.6.0
+    /// Spec v0.6.3
     pub fn get_total_balance(
         &self,
         validator_indices: &[usize],
diff --git a/eth2/types/src/beacon_state/beacon_state_types.rs b/eth2/types/src/beacon_state/beacon_state_types.rs
index 795cc734e..7e4a04258 100644
--- a/eth2/types/src/beacon_state/beacon_state_types.rs
+++ b/eth2/types/src/beacon_state/beacon_state_types.rs
@@ -22,7 +22,7 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq {
 
     /// Return the number of committees in one epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn get_epoch_committee_count(
         active_validator_count: usize,
         target_committee_size: usize,
@@ -60,42 +60,42 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq {
 
     /// Returns the `SLOTS_PER_EPOCH` constant for this specification.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn slots_per_epoch() -> u64 {
         Self::SlotsPerEpoch::to_u64()
     }
 
     /// Returns the `SHARD_COUNT` constant for this specification.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn shard_count() -> usize {
         Self::ShardCount::to_usize()
     }
 
     /// Returns the `SLOTS_PER_HISTORICAL_ROOT` constant for this specification.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn slots_per_historical_root() -> usize {
         Self::SlotsPerHistoricalRoot::to_usize()
     }
 
     /// Returns the `LATEST_RANDAO_MIXES_LENGTH` constant for this specification.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn latest_randao_mixes_length() -> usize {
         Self::LatestRandaoMixesLength::to_usize()
     }
 
     /// Returns the `LATEST_ACTIVE_INDEX_ROOTS` constant for this specification.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn latest_active_index_roots() -> usize {
         Self::LatestActiveIndexRootsLength::to_usize()
     }
 
     /// Returns the `LATEST_SLASHED_EXIT_LENGTH` constant for this specification.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn latest_slashed_exit_length() -> usize {
         Self::LatestSlashedExitLength::to_usize()
     }
@@ -103,7 +103,7 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq {
 
 /// Ethereum Foundation specifications.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(Clone, PartialEq, Debug, Default, Serialize, Deserialize)]
 pub struct MainnetEthSpec;
 
diff --git a/eth2/types/src/beacon_state/committee_cache.rs b/eth2/types/src/beacon_state/committee_cache.rs
index 418213a68..54564d95d 100644
--- a/eth2/types/src/beacon_state/committee_cache.rs
+++ b/eth2/types/src/beacon_state/committee_cache.rs
@@ -24,7 +24,7 @@ pub struct CommitteeCache {
 impl CommitteeCache {
     /// Return a new, fully initialized cache.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn initialized<T: EthSpec>(
         state: &BeaconState<T>,
         epoch: Epoch,
@@ -128,7 +128,7 @@ impl CommitteeCache {
     ///
     /// Always returns `&[]` for a non-initialized epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn active_validator_indices(&self) -> &[usize] {
         &self.shuffling
     }
@@ -137,7 +137,7 @@ impl CommitteeCache {
     ///
     /// Always returns `&[]` for a non-initialized epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn shuffling(&self) -> &[usize] {
         &self.shuffling
     }
@@ -147,7 +147,7 @@ impl CommitteeCache {
     ///
     /// Always returns `None` for a non-initialized epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_crosslink_committee_for_shard(&self, shard: Shard) -> Option<CrosslinkCommittee> {
         if shard >= self.shard_count || self.initialized_epoch.is_none() {
             return None;
@@ -201,7 +201,7 @@ impl CommitteeCache {
     ///
     /// Always returns `usize::default()` for a non-initialized epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn active_validator_count(&self) -> usize {
         self.shuffling.len()
     }
@@ -210,7 +210,7 @@ impl CommitteeCache {
     ///
     /// Always returns `usize::default()` for a non-initialized epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn epoch_committee_count(&self) -> usize {
         self.committee_count
     }
@@ -226,7 +226,7 @@ impl CommitteeCache {
     ///
     /// Returns `None` if `slot` is not in the initialized epoch, or if `Self` is not initialized.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_crosslink_committees_for_slot(&self, slot: Slot) -> Option<Vec<CrosslinkCommittee>> {
         let position = self
             .initialized_epoch?
@@ -258,7 +258,7 @@ impl CommitteeCache {
     ///
     /// Always returns `None` for a non-initialized epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn first_committee_at_slot(&self, slot: Slot) -> Option<&[usize]> {
         self.get_crosslink_committees_for_slot(slot)?
             .first()
@@ -267,7 +267,7 @@ impl CommitteeCache {
 
     /// Returns a slice of `self.shuffling` that represents the `index`'th committee in the epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn compute_committee(&self, index: usize) -> Option<&[usize]> {
         Some(&self.shuffling[self.compute_committee_range(index)?])
     }
@@ -276,7 +276,7 @@ impl CommitteeCache {
     ///
     /// To avoid a divide-by-zero, returns `None` if `self.committee_count` is zero.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn compute_committee_range(&self, index: usize) -> Option<Range<usize>> {
         if self.committee_count == 0 {
             return None;
@@ -295,7 +295,7 @@ impl CommitteeCache {
     ///
     /// Always returns `None` for a non-initialized epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     fn crosslink_slot_for_shard(&self, shard: u64) -> Option<Slot> {
         let offset = (shard + self.shard_count - self.shuffling_start_shard) % self.shard_count;
         Some(
@@ -317,7 +317,7 @@ impl CommitteeCache {
 /// Returns a list of all `validator_registry` indices where the validator is active at the given
 /// `epoch`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub fn get_active_validator_indices(validators: &[Validator], epoch: Epoch) -> Vec<usize> {
     let mut active = Vec::with_capacity(validators.len());
 
@@ -335,7 +335,7 @@ pub fn get_active_validator_indices(validators: &[Validator], epoch: Epoch) -> V
 /// Returns the count of all `validator_registry` indices where the validator is active at the given
 /// `epoch`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 fn get_active_validator_count(validators: &[Validator], epoch: Epoch) -> usize {
     validators.iter().filter(|v| v.is_active_at(epoch)).count()
 }
diff --git a/eth2/types/src/chain_spec.rs b/eth2/types/src/chain_spec.rs
index 16c3d30f3..74ce40671 100644
--- a/eth2/types/src/chain_spec.rs
+++ b/eth2/types/src/chain_spec.rs
@@ -5,7 +5,7 @@ use test_utils::{u8_from_hex_str, u8_to_hex_str};
 
 /// Each of the BLS signature domains.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 pub enum Domain {
     BeaconProposer,
     Randao,
@@ -17,7 +17,7 @@ pub enum Domain {
 
 /// Holds all the "constants" for a BeaconChain.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(PartialEq, Debug, Clone, Serialize, Deserialize)]
 #[serde(default)]
 pub struct ChainSpec {
@@ -115,7 +115,7 @@ pub struct ChainSpec {
 impl ChainSpec {
     /// Get the domain number that represents the fork meta and signature domain.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_domain(&self, epoch: Epoch, domain: Domain, fork: &Fork) -> u64 {
         let domain_constant = match domain {
             Domain::BeaconProposer => self.domain_beacon_proposer,
@@ -137,7 +137,7 @@ impl ChainSpec {
 
     /// Returns a `ChainSpec` compatible with the Ethereum Foundation specification.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn mainnet() -> Self {
         Self {
             /*
diff --git a/eth2/types/src/crosslink.rs b/eth2/types/src/crosslink.rs
index 9a06ca8bf..d7d77ec4a 100644
--- a/eth2/types/src/crosslink.rs
+++ b/eth2/types/src/crosslink.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Specifies the block hash for a shard at an epoch.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/deposit.rs b/eth2/types/src/deposit.rs
index 1b031b0d5..df814c297 100644
--- a/eth2/types/src/deposit.rs
+++ b/eth2/types/src/deposit.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// A deposit to potentially become a beacon chain validator.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/deposit_data.rs b/eth2/types/src/deposit_data.rs
index 274fa68a4..895e47e59 100644
--- a/eth2/types/src/deposit_data.rs
+++ b/eth2/types/src/deposit_data.rs
@@ -10,7 +10,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// The data supplied by the user to the deposit contract.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
@@ -35,7 +35,7 @@ pub struct DepositData {
 impl DepositData {
     /// Generate the signature for a given DepositData details.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn create_signature(
         &self,
         secret_key: &SecretKey,
diff --git a/eth2/types/src/eth1_data.rs b/eth2/types/src/eth1_data.rs
index 0a7043543..dedaf9f00 100644
--- a/eth2/types/src/eth1_data.rs
+++ b/eth2/types/src/eth1_data.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Contains data obtained from the Eth1 chain.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/fork.rs b/eth2/types/src/fork.rs
index 47ff29916..4546fd5f7 100644
--- a/eth2/types/src/fork.rs
+++ b/eth2/types/src/fork.rs
@@ -10,7 +10,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Specifies a fork of the `BeaconChain`, to prevent replay attacks.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
@@ -35,7 +35,7 @@ pub struct Fork {
 impl Fork {
     /// Initialize the `Fork` from the genesis parameters in the `spec`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn genesis(genesis_epoch: Epoch) -> Self {
         Self {
             previous_version: [0; 4],
@@ -46,7 +46,7 @@ impl Fork {
 
     /// Return the fork version of the given ``epoch``.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn get_fork_version(&self, epoch: Epoch) -> [u8; 4] {
         if epoch < self.epoch {
             return self.previous_version;
diff --git a/eth2/types/src/historical_batch.rs b/eth2/types/src/historical_batch.rs
index 0d8916216..30206ae63 100644
--- a/eth2/types/src/historical_batch.rs
+++ b/eth2/types/src/historical_batch.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Historical block and state roots.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/indexed_attestation.rs b/eth2/types/src/indexed_attestation.rs
index 14f6e470b..1758521e1 100644
--- a/eth2/types/src/indexed_attestation.rs
+++ b/eth2/types/src/indexed_attestation.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 ///
 /// To be included in an `AttesterSlashing`.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
@@ -35,14 +35,14 @@ pub struct IndexedAttestation {
 impl IndexedAttestation {
     /// Check if ``attestation_data_1`` and ``attestation_data_2`` have the same target.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn is_double_vote(&self, other: &IndexedAttestation) -> bool {
         self.data.target_epoch == other.data.target_epoch && self.data != other.data
     }
 
     /// Check if ``attestation_data_1`` surrounds ``attestation_data_2``.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn is_surround_vote(&self, other: &IndexedAttestation) -> bool {
         self.data.source_epoch < other.data.source_epoch
             && other.data.target_epoch < self.data.target_epoch
diff --git a/eth2/types/src/pending_attestation.rs b/eth2/types/src/pending_attestation.rs
index 2c3b04a42..53e381a6f 100644
--- a/eth2/types/src/pending_attestation.rs
+++ b/eth2/types/src/pending_attestation.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// An attestation that has been included in the state but not yet fully processed.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/proposer_slashing.rs b/eth2/types/src/proposer_slashing.rs
index b4d5ef0e5..591fdad49 100644
--- a/eth2/types/src/proposer_slashing.rs
+++ b/eth2/types/src/proposer_slashing.rs
@@ -8,7 +8,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Two conflicting proposals from the same proposer (validator).
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,
diff --git a/eth2/types/src/relative_epoch.rs b/eth2/types/src/relative_epoch.rs
index 3178701e8..eeeca65f3 100644
--- a/eth2/types/src/relative_epoch.rs
+++ b/eth2/types/src/relative_epoch.rs
@@ -9,7 +9,7 @@ pub enum Error {
 /// Defines the epochs relative to some epoch. Most useful when referring to the committees prior
 /// to and following some epoch.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(Debug, PartialEq, Clone, Copy)]
 pub enum RelativeEpoch {
     /// The prior epoch.
@@ -23,7 +23,7 @@ pub enum RelativeEpoch {
 impl RelativeEpoch {
     /// Returns the `epoch` that `self` refers to, with respect to the `base` epoch.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn into_epoch(self, base: Epoch) -> Epoch {
         match self {
             // Due to saturating nature of epoch, check for current first.
@@ -40,7 +40,7 @@ impl RelativeEpoch {
     /// - `EpochTooLow` when `other` is more than 1 prior to `base`.
     /// - `EpochTooHigh` when `other` is more than 1 after `base`.
     ///
-    /// Spec v0.6.1
+    /// Spec v0.6.3
     pub fn from_epoch(base: Epoch, other: Epoch) -> Result<Self, Error> {
         // Due to saturating nature of epoch, check for current first.
         if other == base {
diff --git a/eth2/types/src/transfer.rs b/eth2/types/src/transfer.rs
index ffac85c7b..8a7850cfc 100644
--- a/eth2/types/src/transfer.rs
+++ b/eth2/types/src/transfer.rs
@@ -11,7 +11,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// The data submitted to the deposit contract.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/validator.rs b/eth2/types/src/validator.rs
index f16225d7c..4337e164d 100644
--- a/eth2/types/src/validator.rs
+++ b/eth2/types/src/validator.rs
@@ -7,7 +7,7 @@ use tree_hash_derive::{CachedTreeHash, TreeHash};
 
 /// Information about a `BeaconChain` validator.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     Clone,
diff --git a/eth2/types/src/voluntary_exit.rs b/eth2/types/src/voluntary_exit.rs
index 6754aa2c9..5630d4d4c 100644
--- a/eth2/types/src/voluntary_exit.rs
+++ b/eth2/types/src/voluntary_exit.rs
@@ -9,7 +9,7 @@ use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
 
 /// An exit voluntarily submitted a validator who wishes to withdraw.
 ///
-/// Spec v0.6.1
+/// Spec v0.6.3
 #[derive(
     Debug,
     PartialEq,