diff --git a/specs/sharding/beacon-chain.md b/specs/sharding/beacon-chain.md
index 7adc5bb27..c0dab3ad9 100644
--- a/specs/sharding/beacon-chain.md
+++ b/specs/sharding/beacon-chain.md
@@ -223,7 +223,7 @@ class PendingShardHeader(Container):
     # Who voted for the header
     votes: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
     # Has this header been confirmed?
-    confirmed: bool
+    confirmed: boolean
 ```
 
 ## Helper functions