diff --git a/eth2/types/src/beacon_state.rs b/eth2/types/src/beacon_state.rs
index 9bcfa5cec..ec1008d3c 100644
--- a/eth2/types/src/beacon_state.rs
+++ b/eth2/types/src/beacon_state.rs
@@ -129,6 +129,7 @@ pub struct BeaconState {
     #[ssz(skip_deserializing)]
     #[tree_hash(skip_hashing)]
     pub cache_index_offset: usize,
+    #[serde(default)]
     #[ssz(skip_serializing)]
     #[ssz(skip_deserializing)]
     #[tree_hash(skip_hashing)]