diff --git a/src/chart/custom/CustomView.ts b/src/chart/custom/CustomView.ts
index 215087b72b..ad282ed9b0 100644
--- a/src/chart/custom/CustomView.ts
+++ b/src/chart/custom/CustomView.ts
@@ -1340,6 +1340,13 @@ function mergeChildren(
             );
         }
         else {
+            if (__DEV__) {
+                assert(
+                    oldChild,
+                    'renderItem should not return a group containing elements'
+                    + ' as null/undefined/{} if they do not exist before.'
+                );
+            }
             // If the new element option is null, it means to remove the old
             // element. But we cannot really remove the element from the group
             // directly, because the element order may not be stable when this