diff --git a/models/topic.go b/models/topic.go
index 3b37901b9..678795a3d 100644
--- a/models/topic.go
+++ b/models/topic.go
@@ -190,7 +190,7 @@ func SaveTopics(repoID int64, topicNames ...string) error {
 		}
 	}
 
-	topicNames = topicNames[:0]
+	topicNames = make([]string, 0, 25)
 	if err := sess.Table("topic").Cols("name").
 		Join("INNER", "repo_topic", "repo_topic.topic_id = topic.id").
 		Where("repo_topic.repo_id = ?", repoID).Desc("topic.repo_count").Find(&topicNames); err != nil {