diff --git a/src/main/scala/gitbucket/core/util/JDBCUtil.scala b/src/main/scala/gitbucket/core/util/JDBCUtil.scala
index 60ffd2a..34c399d 100644
--- a/src/main/scala/gitbucket/core/util/JDBCUtil.scala
+++ b/src/main/scala/gitbucket/core/util/JDBCUtil.scala
@@ -227,7 +227,7 @@
         if (noPreds.isEmpty) {
           if (hasPreds.isEmpty) done else sys.error(hasPreds.toString)
         } else {
-          val found = noPreds.map { _._1 }
+          val found = noPreds.keys
           tsort(hasPreds.map { case (k, v) => (k, v -- found) }, done ++ found)
         }
       }