diff --git a/eth2/types/src/beacon_state.rs b/eth2/types/src/beacon_state.rs
index 18b5fc989..2bdf85fcc 100644
--- a/eth2/types/src/beacon_state.rs
+++ b/eth2/types/src/beacon_state.rs
@@ -4,6 +4,7 @@ use crate::{
     Bitfield, ChainSpec, Crosslink, Deposit, DepositInput, Epoch, Eth1Data, Eth1DataVote, Fork,
     Hash256, PendingAttestation, PublicKey, Signature, Slot, Validator,
 };
+use bls::verify_proof_of_possession;
 use honey_badger_split::SplitExt;
 use log::trace;
 use rand::RngCore;
@@ -389,6 +390,7 @@ impl BeaconState {
         &self,
         slot: Slot,
         registry_change: bool,
+
         spec: &ChainSpec,
     ) -> Result<Vec<(Vec<usize>, u64)>, BeaconStateError> {
         let epoch = slot.epoch(spec.epoch_length);
@@ -668,12 +670,17 @@ impl BeaconState {
         withdrawal_credentials: Hash256,
         spec: &ChainSpec,
     ) -> Result<usize, ()> {
-        if !self.validate_proof_of_possession(
-            pubkey.clone(),
-            proof_of_possession,
-            withdrawal_credentials,
-            &spec,
-        ) {
+        // TODO: update proof of possession to function written above (
+        // requires bls::create_proof_of_possession to be updated
+        // https://github.com/sigp/lighthouse/issues/239
+        if !verify_proof_of_possession(&proof_of_possession, &pubkey)
+        //if !self.validate_proof_of_possession(
+        //    pubkey.clone(),
+        //    proof_of_possession,
+        //    withdrawal_credentials,
+        //    &spec,
+        //    )
+        {
             return Err(());
         }
 
diff --git a/eth2/utils/bls/src/lib.rs b/eth2/utils/bls/src/lib.rs
index 074929b32..4d0864a90 100644
--- a/eth2/utils/bls/src/lib.rs
+++ b/eth2/utils/bls/src/lib.rs
@@ -16,7 +16,7 @@ pub use crate::signature::Signature;
 
 pub use self::bls_aggregates::AggregatePublicKey;
 
-pub const BLS_AGG_SIG_BYTE_SIZE: usize = 97;
+pub const BLS_AGG_SIG_BYTE_SIZE: usize = 96;
 
 use hashing::hash;
 use ssz::ssz_encode;
@@ -29,7 +29,14 @@ fn extend_if_needed(hash: &mut Vec<u8>) {
 
 /// For some signature and public key, ensure that the signature message was the public key and it
 /// was signed by the secret key that corresponds to that public key.
+pub fn verify_proof_of_possession(sig: &Signature, pubkey: &PublicKey) -> bool {
+    // TODO: replace this function with state.validate_proof_of_possession
+    // https://github.com/sigp/lighthouse/issues/239
+    sig.verify(&ssz_encode(pubkey), 0, &pubkey)
+}
 
+// TODO: Update this method
+// https://github.com/sigp/lighthouse/issues/239
 pub fn create_proof_of_possession(keypair: &Keypair) -> Signature {
     Signature::new(&ssz_encode(&keypair.pk), 0, &keypair.sk)
 }
@@ -40,6 +47,5 @@ pub fn bls_verify_aggregate(
     signature: &AggregateSignature,
     domain: u64,
 ) -> bool {
-    // TODO: add domain
     signature.verify(message, domain, pubkey)
 }