diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index e7eee3809..e21784656 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -857,7 +857,7 @@ def get_block_hash(state: BeaconState,
 #### `get_beacon_proposer_index`
 
 ```python
-def get_beacon_proposer_index(state:BeaconState,
+def get_beacon_proposer_index(state: BeaconState,
                               slot: int) -> int:
     """
     Returns the beacon proposer index for the ``slot``.