diff --git a/specs/phase1/beacon-chain.md b/specs/phase1/beacon-chain.md
index 7737aa9ea..ccfbed3db 100644
--- a/specs/phase1/beacon-chain.md
+++ b/specs/phase1/beacon-chain.md
@@ -191,7 +191,7 @@ class ShardHeader(Container):
 ```python
 class PendingShardHeader(Container):
     # Slot and shard that this header is intended for
-    slot: uint64
+    slot: Slot
     shard: Shard
     # Kate commitment to the data
     commitment: BLSCommitment