diff --git a/specs/altair/p2p-interface.md b/specs/altair/p2p-interface.md
index df2955f13..6f250b57e 100644
--- a/specs/altair/p2p-interface.md
+++ b/specs/altair/p2p-interface.md
@@ -108,7 +108,7 @@ The following validations MUST pass before forwarding the `signed_contribution_a
 def get_sync_subcommittee_pubkeys(state: BeaconState, subcommittee_index: uint64) -> Sequence[BLSPubkey]:
     # Committees assigned to `slot` sign for `slot - 1`
     # This creates the exceptional logic below when transitioning between sync committee periods
-    next_slot_epoch = compute_epoch_at_slot(state.slot + 1)
+    next_slot_epoch = compute_epoch_at_slot(Slot(state.slot + 1))
     if compute_sync_committee_period(get_current_epoch(state)) == compute_sync_committee_period(next_slot_epoch):
         sync_committee = state.current_sync_committee
     else: