diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index b2813a2d9..ca35679ed 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -127,7 +127,7 @@ class ApplicationPayload(Container):
 #### `is_transition_completed`
 
 ```python
-def is_transition_completed(state: BeaconState) -> Boolean:
+def is_transition_completed(state: BeaconState) -> boolean:
     state.application_block_hash != Bytes32()
 ```