diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 317d929c9..8bfc52993 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -2370,7 +2370,7 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     """
     # Can't submit attestations that are too far in history (or in prehistory) 
     assert attestation.data.slot >= GENESIS_SLOT
-    assert state.slot < attestation.data.slot + SLOTS_PER_EPOCH
+    assert state.slot <= attestation.data.slot + SLOTS_PER_EPOCH
     # Can't submit attestations too quickly
     assert attestation.data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot
     # Verify that the justified epoch is correct, case 1: current epoch attestations