diff --git a/db/cuckoo_table_db_test.cc b/db/cuckoo_table_db_test.cc
index 2652d1776..4beee59e4 100644
--- a/db/cuckoo_table_db_test.cc
+++ b/db/cuckoo_table_db_test.cc
@@ -218,6 +218,7 @@ TEST(CuckooTableDBTest, Uint64Comparator) {
 
   // Add more keys.
   ASSERT_OK(Delete(Uint64Key(2)));  // Delete.
+  dbfull()->TEST_FlushMemTable();
   ASSERT_OK(Put(Uint64Key(3), "v0"));  // Update.
   ASSERT_OK(Put(Uint64Key(4), "v4"));
   dbfull()->TEST_FlushMemTable();