diff --git a/etcdserver/api/v3rpc/maintenance.go b/etcdserver/api/v3rpc/maintenance.go
index 3657d0360829..bfe574e579e9 100644
--- a/etcdserver/api/v3rpc/maintenance.go
+++ b/etcdserver/api/v3rpc/maintenance.go
@@ -71,6 +71,10 @@ func (ms *maintenanceServer) Defragment(ctx context.Context, sr *pb.DefragmentRe
 		plog.Errorf("failed to defragment the storage backend (%v)", err)
 		return nil, err
 	}
+
+	// force a write transaction to update the mvcc db size metrics
+	ms.kg.KV().Write().End()
+
 	plog.Noticef("finished defragmenting the storage backend")
 	return &pb.DefragmentResponse{}, nil
 }