diff --git a/models/migrations/v18.go b/models/migrations/v18.go
new file mode 100644
index 000000000..86f97c7e9
--- /dev/null
+++ b/models/migrations/v18.go
@@ -0,0 +1,14 @@
+// Copyright 2017 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"github.com/go-xorm/xorm"
+)
+
+func cleanUnlinkedWebhookAndHookTasks(x *xorm.Engine) error {
+	_, err := x.Exec(`DELETE FROM webhook WHERE (SELECT COUNT(*) FROM repository WHERE id = webhook.repo_id)=0;DELETE FROM hook_task WHERE (SELECT COUNT(*) FROM repository WHERE id = hook_task.repo_id)=0;`)
+	return err
+}