diff --git a/source/core/Backend.hpp b/source/core/Backend.hpp
index 0bf11599..e2b79eef 100644
--- a/source/core/Backend.hpp
+++ b/source/core/Backend.hpp
@@ -115,9 +115,7 @@ public:
     /**
      * @brief callback after resize ops.
      */
-    virtual ErrorCode onResizeEnd() {
-        return MNN::NO_ERROR;
-    }
+    virtual ErrorCode onResizeEnd() = 0;
 
     /**
      * @brief callback before executing ops.