diff --git a/specs/phase1/beacon-chain.md b/specs/phase1/beacon-chain.md
index 73aa9b7da..f14fc96f5 100644
--- a/specs/phase1/beacon-chain.md
+++ b/specs/phase1/beacon-chain.md
@@ -868,7 +868,7 @@ def apply_shard_transition(state: BeaconState, shard: Shard, transition: ShardTr
     assert optional_aggregate_verify(pubkeys, signing_roots, transition.proposer_signature_aggregate)
 
     # Save updated state
-    shard_state = transition.shard_states[len(transition.shard_states) - 1].copy()
+    shard_state = copy(transition.shard_states[len(transition.shard_states) - 1])
     shard_state.slot = compute_previous_slot(state.slot)
     state.shard_states[shard] = shard_state
 ```