diff --git a/models/consistency.go b/models/consistency.go
index 3a5c4cae50d..d8abdd13339 100644
--- a/models/consistency.go
+++ b/models/consistency.go
@@ -297,11 +297,15 @@ func CountOrphanedObjects(subject, refobject, joinCond string) (int64, error) {
 
 // DeleteOrphanedObjects delete subjects with have no existing refobject anymore
 func DeleteOrphanedObjects(subject, refobject, joinCond string) error {
-	_, err := x.In("id", builder.Select("`"+subject+"`.id").
+	subQuery := builder.Select("`"+subject+"`.id").
 		From("`"+subject+"`").
 		Join("LEFT", "`"+refobject+"`", joinCond).
-		Where(builder.IsNull{"`" + refobject + "`.id"})).
-		Delete("`" + subject + "`")
+		Where(builder.IsNull{"`" + refobject + "`.id"})
+	sql, args, err := builder.Delete(builder.In("id", subQuery)).From("`" + subject + "`").ToSQL()
+	if err != nil {
+		return err
+	}
+	_, err = x.Exec(append([]interface{}{sql}, args...)...)
 	return err
 }
 
diff --git a/models/consistency_test.go b/models/consistency_test.go
new file mode 100644
index 00000000000..0a91d9f3dae
--- /dev/null
+++ b/models/consistency_test.go
@@ -0,0 +1,32 @@
+// Copyright 2021 Gitea. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package models
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDeleteOrphanedObjects(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+
+	countBefore, err := x.Count(&PullRequest{})
+	assert.NoError(t, err)
+
+	_, err = x.Insert(&PullRequest{IssueID: 1000}, &PullRequest{IssueID: 1001}, &PullRequest{IssueID: 1003})
+	assert.NoError(t, err)
+
+	orphaned, err := CountOrphanedObjects("pull_request", "issue", "pull_request.issue_id=issue.id")
+	assert.NoError(t, err)
+	assert.EqualValues(t, 3, orphaned)
+
+	err = DeleteOrphanedObjects("pull_request", "issue", "pull_request.issue_id=issue.id")
+	assert.NoError(t, err)
+
+	countAfter, err := x.Count(&PullRequest{})
+	assert.NoError(t, err)
+	assert.EqualValues(t, countBefore, countAfter)
+}