diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 15d1a4b8a..7617f18a6 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -565,7 +565,7 @@ Note: The definitions below are for specification purposes and are not necessari
 #### `get_active_validator_indices`
 
 ```python
-def get_active_validator_indices(validators: [ValidatorRecords]) -> List[int]:
+def get_active_validator_indices(validators: [ValidatorRecord]) -> List[int]:
     """
     Gets indices of active validators from ``validators``.
     """