diff --git a/mongo/mongo.go b/mongo/mongo.go
index c86cb62..c262864 100644
--- a/mongo/mongo.go
+++ b/mongo/mongo.go
@@ -498,7 +498,10 @@ func (m *MongoDB) Update(ctx context.Context, filter bson.M, update bson.M, coll
 			}
 		}
 	}
-	setDoc := update["$set"].(bson.M)
+	setDoc := bson.M{}
+	if !g.IsEmpty(update["$set"]) {
+		setDoc = update["$set"].(bson.M)
+	}
 	if !g.IsEmpty(user.UserName) {
 		setDoc["updater"] = user.UserName
 	}