diff --git a/specs/phase1/shard-transition.md b/specs/phase1/shard-transition.md
index df521e451..f3a1f83ce 100644
--- a/specs/phase1/shard-transition.md
+++ b/specs/phase1/shard-transition.md
@@ -72,14 +72,13 @@ The post-state corresponding to a pre-state `shard_state` and a signed block `si
 def shard_state_transition(shard_state: ShardState,
                            signed_block: SignedShardBlock,
                            beacon_parent_state: BeaconState,
-                           validate_result: bool = True) -> ShardState:
+                           validate_result: bool = True) -> None:
     assert verify_shard_block_message(beacon_parent_state, shard_state, signed_block.message)
 
     if validate_result:
         assert verify_shard_block_signature(beacon_parent_state, signed_block)
 
     process_shard_block(shard_state, signed_block.message)
-    return shard_state
 ```
 
 ```python