diff --git a/integrations/api_issue_label_test.go b/integrations/api_issue_label_test.go
new file mode 100644
index 0000000000..2014d38e7d
--- /dev/null
+++ b/integrations/api_issue_label_test.go
@@ -0,0 +1,64 @@
+// Copyright 2017 The Gitea 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 integrations
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"code.gitea.io/gitea/models"
+	api "code.gitea.io/sdk/gitea"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAPIAddIssueLabels(t *testing.T) {
+	assert.NoError(t, models.LoadFixtures())
+
+	repo := models.AssertExistsAndLoadBean(t, &models.Repository{ID: 1}).(*models.Repository)
+	issue := models.AssertExistsAndLoadBean(t, &models.Issue{RepoID: repo.ID}).(*models.Issue)
+	label := models.AssertExistsAndLoadBean(t, &models.Label{RepoID: repo.ID}).(*models.Label)
+	owner := models.AssertExistsAndLoadBean(t, &models.User{ID: repo.OwnerID}).(*models.User)
+
+	urlStr := fmt.Sprintf("/api/v1/repos/%s/%s/issues/%d/labels",
+		owner.Name, repo.Name, issue.Index)
+	req := NewRequestWithJSON(t, "POST", urlStr, &api.IssueLabelsOption{
+		Labels: []int64{label.ID},
+	})
+	session := loginUser(t, owner.Name)
+	resp := session.MakeRequest(t, req)
+	assert.EqualValues(t, http.StatusOK, resp.HeaderCode)
+	var apiLabels []*api.Label
+	DecodeJSON(t, resp, &apiLabels)
+	assert.Len(t, apiLabels, models.GetCount(t, &models.IssueLabel{IssueID: issue.ID}))
+
+	models.AssertExistsAndLoadBean(t, &models.IssueLabel{IssueID: issue.ID, LabelID: label.ID})
+}
+
+func TestAPIReplaceIssueLabels(t *testing.T) {
+	assert.NoError(t, models.LoadFixtures())
+
+	repo := models.AssertExistsAndLoadBean(t, &models.Repository{ID: 1}).(*models.Repository)
+	issue := models.AssertExistsAndLoadBean(t, &models.Issue{RepoID: repo.ID}).(*models.Issue)
+	label := models.AssertExistsAndLoadBean(t, &models.Label{RepoID: repo.ID}).(*models.Label)
+	owner := models.AssertExistsAndLoadBean(t, &models.User{ID: repo.OwnerID}).(*models.User)
+
+	urlStr := fmt.Sprintf("/api/v1/repos/%s/%s/issues/%d/labels",
+		owner.Name, repo.Name, issue.Index)
+	req := NewRequestWithJSON(t, "PUT", urlStr, &api.IssueLabelsOption{
+		Labels: []int64{label.ID},
+	})
+	session := loginUser(t, owner.Name)
+	resp := session.MakeRequest(t, req)
+	assert.EqualValues(t, http.StatusOK, resp.HeaderCode)
+	var apiLabels []*api.Label
+	DecodeJSON(t, resp, &apiLabels)
+	assert.Len(t, apiLabels, 1)
+	assert.EqualValues(t, label.ID, apiLabels[0].ID)
+
+	models.AssertCount(t, &models.IssueLabel{IssueID: issue.ID}, 1)
+	models.AssertExistsAndLoadBean(t, &models.IssueLabel{IssueID: issue.ID, LabelID: label.ID})
+}
diff --git a/integrations/integration_test.go b/integrations/integration_test.go
index e935d36f19..84b05cb644 100644
--- a/integrations/integration_test.go
+++ b/integrations/integration_test.go
@@ -229,7 +229,9 @@ func NewRequestWithValues(t testing.TB, method, urlStr string, values map[string
 func NewRequestWithJSON(t testing.TB, method, urlStr string, v interface{}) *http.Request {
 	jsonBytes, err := json.Marshal(v)
 	assert.NoError(t, err)
-	return NewRequestWithBody(t, method, urlStr, bytes.NewBuffer(jsonBytes))
+	req := NewRequestWithBody(t, method, urlStr, bytes.NewBuffer(jsonBytes))
+	req.Header.Add("Content-Type", "application/json")
+	return req
 }
 
 func NewRequestWithBody(t testing.TB, method, urlStr string, body io.Reader) *http.Request {
diff --git a/routers/api/v1/repo/issue_label.go b/routers/api/v1/repo/issue_label.go
index d94d666714..2eec743e70 100644
--- a/routers/api/v1/repo/issue_label.go
+++ b/routers/api/v1/repo/issue_label.go
@@ -66,7 +66,7 @@ func AddIssueLabels(ctx *context.APIContext, form api.IssueLabelsOption) {
 
 	apiLabels := make([]*api.Label, len(labels))
 	for i := range labels {
-		apiLabels[i] = issue.Labels[i].APIFormat()
+		apiLabels[i] = labels[i].APIFormat()
 	}
 	ctx.JSON(200, &apiLabels)
 }
@@ -142,7 +142,7 @@ func ReplaceIssueLabels(ctx *context.APIContext, form api.IssueLabelsOption) {
 
 	apiLabels := make([]*api.Label, len(labels))
 	for i := range labels {
-		apiLabels[i] = issue.Labels[i].APIFormat()
+		apiLabels[i] = labels[i].APIFormat()
 	}
 	ctx.JSON(200, &apiLabels)
 }