diff --git a/internal/datacoord/index_service.go b/internal/datacoord/index_service.go
index 4b754f86791fd..add0e93016b2d 100644
--- a/internal/datacoord/index_service.go
+++ b/internal/datacoord/index_service.go
@@ -817,7 +817,7 @@ func (s *Server) DropIndex(ctx context.Context, req *indexpb.DropIndexRequest) (
 	indexes := s.meta.indexMeta.GetIndexesForCollection(req.GetCollectionID(), req.GetIndexName())
 	if len(indexes) == 0 {
 		log.Info(fmt.Sprintf("there is no index on collection: %d with the index name: %s", req.CollectionID, req.IndexName))
-		return merr.Success(), nil
+		return merr.Status(merr.ErrIndexNotFound), nil
 	}
 
 	if !req.GetDropAll() && len(indexes) > 1 {
diff --git a/internal/rootcoord/drop_collection_task.go b/internal/rootcoord/drop_collection_task.go
index ce458e5cff059..d0268d427a4af 100644
--- a/internal/rootcoord/drop_collection_task.go
+++ b/internal/rootcoord/drop_collection_task.go
@@ -60,7 +60,7 @@ func (t *dropCollectionTask) Execute(ctx context.Context) error {
 	if errors.Is(err, merr.ErrCollectionNotFound) {
 		// make dropping collection idempotent.
 		log.Warn("drop non-existent collection", zap.String("collection", t.Req.GetCollectionName()))
-		return nil
+		return merr.ErrCollectionNotFound
 	}
 
 	if err != nil {
diff --git a/internal/rootcoord/drop_partition_task.go b/internal/rootcoord/drop_partition_task.go
index cc45422db7f7e..9e06171b95933 100644
--- a/internal/rootcoord/drop_partition_task.go
+++ b/internal/rootcoord/drop_partition_task.go
@@ -29,6 +29,7 @@ import (
 	"github.com/milvus-io/milvus/internal/util/proxyutil"
 	"github.com/milvus-io/milvus/pkg/common"
 	"github.com/milvus-io/milvus/pkg/log"
+	"github.com/milvus-io/milvus/pkg/util/merr"
 )
 
 type dropPartitionTask struct {
@@ -64,7 +65,7 @@ func (t *dropPartitionTask) Execute(ctx context.Context) error {
 	if partID == common.InvalidPartitionID {
 		log.Warn("drop an non-existent partition", zap.String("collection", t.Req.GetCollectionName()), zap.String("partition", t.Req.GetPartitionName()))
 		// make dropping partition idempotent.
-		return nil
+		return merr.ErrPartitionNotFound
 	}
 
 	redoTask := newBaseRedoTask(t.core.stepExecutor)