diff --git a/ydb/core/tablet_flat/ut/flat_test_db.h b/ydb/core/tablet_flat/ut/flat_test_db.h
index e8b22f0827ec..1b441eff2187 100644
--- a/ydb/core/tablet_flat/ut/flat_test_db.h
+++ b/ydb/core/tablet_flat/ut/flat_test_db.h
@@ -109,7 +109,7 @@ class TFlatDbWrapper : public ITestDb {
 
     void Init(const TScheme& scheme) override {
         Y_UNUSED(scheme);
-        Y_ENSURE("Not supported by flat db wrapper");
+        Y_ENSURE(false, "Not supported by flat db wrapper");
     }
 
     const TScheme& GetScheme() const override {
@@ -118,7 +118,7 @@ class TFlatDbWrapper : public ITestDb {
 
     TString FinishTransaction(bool commit) override {
         Y_UNUSED(commit);
-        Y_ENSURE("Not supported by flat db wrapper");
+        Y_ENSURE(false, "Not supported by flat db wrapper");
         return "42";
     }