diff --git a/specs/core/1_beacon-chain-misc.md b/specs/core/1_beacon-chain-misc.md
index ee63eca64..9e9bfddb9 100644
--- a/specs/core/1_beacon-chain-misc.md
+++ b/specs/core/1_beacon-chain-misc.md
@@ -147,7 +147,7 @@ def process_shard_receipt_proof(state: BeaconState, receipt_proof: ShardReceiptP
     Processes a ShardReceipt object.
     """
     receipt_slot = state.next_shard_receipt_period[receipt_proof.shard] * SLOTS_PER_EPOCH * EPOCHS_PER_SHARD_PERIOD
-    first_slot_in_last_crosslink = state.current_crosslinks[receipt_proof.shard].start_epoch * SLOTS_PER_EPOCH
+    first_slot_in_last_crosslink = state.current_crosslinks[receipt_proof.shard].start_epoch * SHARD_SLOTS_PER_BEACON_SLOT * SLOTS_PER_EPOCH
     gindex = concat_generalized_indices(
         get_generalized_index_of_crosslink_header(0),
         GeneralizedIndex(get_generalized_index(ShardBlockHeader, 'state_root')),