diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index afa87a140..25eb7bbe6 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -992,7 +992,7 @@ def get_randao_mix(state: BeaconState,
 
 ```python
 def get_active_index_root(state: BeaconState,
-                          slot: int) -> Hash32:
+                          slot: int) -> Bytes32:
     """
     Returns the index root at a recent ``slot``.
     """