diff --git a/specs/phase1/beacon-chain.md b/specs/phase1/beacon-chain.md
index fccf157aa..4a75cb076 100644
--- a/specs/phase1/beacon-chain.md
+++ b/specs/phase1/beacon-chain.md
@@ -476,7 +476,7 @@ def get_online_validator_indices(state: BeaconState) -> Set[ValidatorIndex]:
 ```python
 def get_shard_committee(beacon_state: BeaconState, epoch: Epoch, shard: Shard) -> Sequence[ValidatorIndex]:
     source_epoch = epoch - epoch % SHARD_COMMITTEE_PERIOD
-    if source_epoch > SHARD_COMMITTEE_PERIOD:
+    if source_epoch >= SHARD_COMMITTEE_PERIOD:
         source_epoch -= SHARD_COMMITTEE_PERIOD
     active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
     seed = get_seed(beacon_state, source_epoch, DOMAIN_SHARD_COMMITTEE)