diff --git a/mempool/v1/mempool.go b/mempool/v1/mempool.go
index f84b20553..135ce19d3 100644
--- a/mempool/v1/mempool.go
+++ b/mempool/v1/mempool.go
@@ -395,12 +395,11 @@ func (txmp *TxMempool) Update(
 	newPreFn mempool.PreCheckFunc,
 	newPostFn mempool.PostCheckFunc,
 ) error {
-	// TODO(creachadair): This would be a nice safety check but requires Go 1.18.
-	// // Safety check: The caller is required to hold the lock.
-	// if txmp.mtx.TryLock() {
-	// 	txmp.mtx.Unlock()
-	// 	panic("mempool: Update caller does not hold the lock")
-	// }
+	// Safety sanity check: The caller is required to hold the lock.
+	if txmp.mtx.TryLock() {
+		txmp.mtx.Unlock()
+		panic("mempool: Update caller does not hold the lock")
+	}
 	// Safety check: Transactions and responses must match in number.
 	if len(blockTxs) != len(deliverTxResponses) {
 		panic(fmt.Sprintf("mempool: got %d transactions but %d DeliverTx responses",