diff --git a/x-pack/plugins/transform/public/app/sections/create_transform/components/step_define/hooks/use_pivot_config.ts b/x-pack/plugins/transform/public/app/sections/create_transform/components/step_define/hooks/use_pivot_config.ts
index 4616b3368e824b..d35d567fc84695 100644
--- a/x-pack/plugins/transform/public/app/sections/create_transform/components/step_define/hooks/use_pivot_config.ts
+++ b/x-pack/plugins/transform/public/app/sections/create_transform/components/step_define/hooks/use_pivot_config.ts
@@ -211,9 +211,11 @@ export const usePivotConfig = (
         throw new Error('No parent aggregation reference found');
       }
 
+      const { [prevSubItemName]: deleted, ...newSubAgg } = parent.subAggs;
+
       const aggNameConflictMessages = getAggNameConflictToastMessages(
         subItem.aggName,
-        parent.subAggs,
+        newSubAgg,
         {}
       );
       if (aggNameConflictMessages.length > 0) {
@@ -221,7 +223,6 @@ export const usePivotConfig = (
         return;
       }
 
-      const { [prevSubItemName]: deleted, ...newSubAgg } = parent.subAggs;
       parent.subAggs = {
         ...newSubAgg,
         [subItem.aggName]: subItem,