diff --git a/types/mempool/mempool.go b/types/mempool/mempool.go
index b64083562c67..5e4fd0aa07e1 100644
--- a/types/mempool/mempool.go
+++ b/types/mempool/mempool.go
@@ -32,8 +32,7 @@ type Mempool interface {
 	InsertWithGasWanted(context.Context, sdk.Tx, uint64) error
 
 	// Select returns an Iterator over the app-side mempool. If txs are specified,
-	// then they shall be incorporated into the Iterator. The Iterator must
-	// closed by the caller.
+	// then they shall be incorporated into the Iterator. The Iterator is not thread-safe to use.
 	Select(context.Context, [][]byte) Iterator
 
 	// SelectBy use callback to iterate over the mempool.