diff --git a/models/pull_list.go b/models/pull_list.go
index 7c5b83ae5f275..c4621afbac3a8 100644
--- a/models/pull_list.go
+++ b/models/pull_list.go
@@ -59,6 +59,16 @@ func GetUnmergedPullRequestsByHeadInfo(repoID int64, branch string) ([]*PullRequ
 		Find(&prs)
 }
 
+// CheckUnmergedPullRequestsByHeadInfo check if the pull requests that are open and has not been merged
+// by given head information (repo and branch) exist.
+func CheckUnmergedPullRequestsByHeadInfo(repoID int64, branch string) (bool, error) {
+	return db.GetEngine(db.DefaultContext).
+		Where("head_repo_id = ? AND head_branch = ? AND has_merged = ? AND issue.is_closed = ? AND flow = ?",
+			repoID, branch, false, false, PullRequestFlowGithub).
+		Join("INNER", "issue", "issue.id = pull_request.issue_id").
+		Exist(&PullRequest{})
+}
+
 // GetUnmergedPullRequestsByBaseInfo returns all pull requests that are open and has not been merged
 // by given base information (repo and branch).
 func GetUnmergedPullRequestsByBaseInfo(repoID int64, branch string) ([]*PullRequest, error) {
diff --git a/models/pull_test.go b/models/pull_test.go
index f5e9d486ff79e..ec4a172f4d05e 100644
--- a/models/pull_test.go
+++ b/models/pull_test.go
@@ -107,6 +107,18 @@ func TestGetUnmergedPullRequest(t *testing.T) {
 	assert.True(t, IsErrPullRequestNotExist(err))
 }
 
+func TestCheckUnmergedPullRequestsByHeadInfo(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	exist, err := CheckUnmergedPullRequestsByHeadInfo(1, "branch2")
+	assert.NoError(t, err)
+	assert.Equal(t, true, exist)
+
+	exist, err = CheckUnmergedPullRequestsByHeadInfo(1, "not_exist_branch")
+	assert.NoError(t, err)
+	assert.Equal(t, false, exist)
+}
+
 func TestGetUnmergedPullRequestsByHeadInfo(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 	prs, err := GetUnmergedPullRequestsByHeadInfo(1, "branch2")
diff --git a/routers/api/v1/repo/pull.go b/routers/api/v1/repo/pull.go
index 28c9bb11c3d4a..2428f145db623 100644
--- a/routers/api/v1/repo/pull.go
+++ b/routers/api/v1/repo/pull.go
@@ -874,12 +874,12 @@ func MergePullRequest(ctx *context.APIContext) {
 
 	if form.DeleteBranchAfterMerge {
 		// Don't cleanup when other pr use this branch as head branch
-		prs, err := models.GetUnmergedPullRequestsByHeadInfo(pr.HeadRepoID, pr.HeadBranch)
+		exist, err := models.CheckUnmergedPullRequestsByHeadInfo(pr.HeadRepoID, pr.HeadBranch)
 		if err != nil {
-			ctx.ServerError("GetUnmergedPullRequestsByHeadInfo", err)
+			ctx.ServerError("CheckUnmergedPullRequestsByHeadInfo", err)
 			return
 		}
-		if len(prs) > 0 {
+		if exist {
 			ctx.Status(http.StatusOK)
 			return
 		}
diff --git a/routers/web/repo/issue.go b/routers/web/repo/issue.go
index f9f903e113cf3..2ff5982549e83 100644
--- a/routers/web/repo/issue.go
+++ b/routers/web/repo/issue.go
@@ -1607,13 +1607,13 @@ func ViewIssue(ctx *context.Context) {
 			(!pull.HasMerged || ctx.Data["HeadBranchCommitID"] == ctx.Data["PullHeadCommitID"])
 
 		if isPullBranchDeletable && pull.HasMerged {
-			prs, err := models.GetUnmergedPullRequestsByHeadInfo(pull.HeadRepoID, pull.HeadBranch)
+			exist, err := models.CheckUnmergedPullRequestsByHeadInfo(pull.HeadRepoID, pull.HeadBranch)
 			if err != nil {
-				ctx.ServerError("GetUnmergedPullRequestsByHeadInfo", err)
+				ctx.ServerError("CheckUnmergedPullRequestsByHeadInfo", err)
 				return
 			}
 
-			isPullBranchDeletable = len(prs) == 0
+			isPullBranchDeletable = !exist
 		}
 		ctx.Data["IsPullBranchDeletable"] = isPullBranchDeletable
 
diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index b16e0da4f6d94..33ec4ffbc80c3 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -1053,12 +1053,12 @@ func MergePullRequest(ctx *context.Context) {
 
 	if form.DeleteBranchAfterMerge {
 		// Don't cleanup when other pr use this branch as head branch
-		prs, err := models.GetUnmergedPullRequestsByHeadInfo(pr.HeadRepoID, pr.HeadBranch)
+		exist, err := models.CheckUnmergedPullRequestsByHeadInfo(pr.HeadRepoID, pr.HeadBranch)
 		if err != nil {
-			ctx.ServerError("GetUnmergedPullRequestsByHeadInfo", err)
+			ctx.ServerError("CheckUnmergedPullRequestsByHeadInfo", err)
 			return
 		}
-		if len(prs) > 0 {
+		if exist {
 			ctx.Redirect(issue.Link())
 			return
 		}
@@ -1273,12 +1273,12 @@ func CleanUpPullRequest(ctx *context.Context) {
 	}
 
 	// Don't cleanup when other pr use this branch as head branch
-	prs, err := models.GetUnmergedPullRequestsByHeadInfo(pr.HeadRepoID, pr.HeadBranch)
+	exist, err := models.CheckUnmergedPullRequestsByHeadInfo(pr.HeadRepoID, pr.HeadBranch)
 	if err != nil {
-		ctx.ServerError("GetUnmergedPullRequestsByHeadInfo", err)
+		ctx.ServerError("CheckUnmergedPullRequestsByHeadInfo", err)
 		return
 	}
-	if len(prs) > 0 {
+	if exist {
 		ctx.NotFound("CleanUpPullRequest", nil)
 		return
 	}