diff --git a/ee/app/controllers/projects/integrations/zentao/issues_controller.rb b/ee/app/controllers/projects/integrations/zentao/issues_controller.rb
index c751652f7f50bb0a278f3d2dd1bfef1c62366c3d..dc1927eeb8646382b603468091cac1431247cb8f 100644
--- a/ee/app/controllers/projects/integrations/zentao/issues_controller.rb
+++ b/ee/app/controllers/projects/integrations/zentao/issues_controller.rb
@@ -59,8 +59,15 @@ def check_feature_enabled!
         def render_error(exception)
           log_exception(exception)
 
-          render json: { errors: [s_('ZentaoIntegration|An error occurred while requesting data from the ZenTao service.')] },
-            status: :bad_request
+          respond_to do |format|
+            format.html do
+              render action_name
+            end
+            format.json do
+              render json: { errors: [s_('ZentaoIntegration|An error occurred while requesting data from the ZenTao service.')] },
+                status: :bad_request
+            end
+          end
         end
       end
     end
diff --git a/ee/app/views/projects/integrations/zentao/issues/show.html.haml b/ee/app/views/projects/integrations/zentao/issues/show.html.haml
index 7cf23a924bbbe87b1b6d45df13c2cea5d9351dec..3882ff7055c7741e2c7f52dfef1b62d2be5672e6 100644
--- a/ee/app/views/projects/integrations/zentao/issues/show.html.haml
+++ b/ee/app/views/projects/integrations/zentao/issues/show.html.haml
@@ -1,5 +1,6 @@
 - add_to_breadcrumbs s_('ZentaoIntegration|ZenTao issues'), project_integrations_zentao_issues_path(@project)
-- breadcrumb_title zentao_issue_breadcrumb_link(@issue_json)
-- page_title html_escape(@issue_json[:title])
+- if @issue_json.present?
+  - breadcrumb_title zentao_issue_breadcrumb_link(@issue_json)
+  - page_title html_escape(@issue_json[:title])
 
 .js-zentao-issues-show-app{ data: zentao_issues_show_data }
diff --git a/ee/spec/controllers/projects/integrations/zentao/issues_controller_spec.rb b/ee/spec/controllers/projects/integrations/zentao/issues_controller_spec.rb
index f60bd94ee8c15332f31789c9c0690be64922eb81..95042e77ed6d4fb1764e04b813d1d0c130631f4b 100644
--- a/ee/spec/controllers/projects/integrations/zentao/issues_controller_spec.rb
+++ b/ee/spec/controllers/projects/integrations/zentao/issues_controller_spec.rb
@@ -94,18 +94,42 @@
         end
       end
 
-      it 'renders `show` template' do
-        get :show, params: { namespace_id: project.namespace, project_id: project, id: 'story-1' }
+      context 'with valid request' do
+        it 'renders `show` template successfully' do
+          get :show, params: { namespace_id: project.namespace, project_id: project, id: 'story-1' }
+
+          expect(assigns(:issue_json)).to eq(issue_json)
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to render_template(:show)
+        end
 
-        expect(assigns(:issue_json)).to eq(issue_json)
-        expect(response).to have_gitlab_http_status(:ok)
-        expect(response).to render_template(:show)
+        it 'returns JSON response successfully' do
+          get :show, params: { namespace_id: project.namespace, project_id: project, id: 'story-1', format: :json }
+
+          expect(json_response).to eq(issue_json)
+        end
       end
 
-      it 'returns JSON response' do
-        get :show, params: { namespace_id: project.namespace, project_id: project, id: 'story-1', format: :json }
+      context 'with bad request' do
+        before do
+          allow_next_instance_of(Integrations::ZentaoSerializers::IssueDetailSerializer) do |serializer|
+            allow(serializer).to receive(:represent).and_raise(::Gitlab::Zentao::Client::Error)
+          end
+        end
+        it 'renders `show` template successfully' do
+          get :show, params: { namespace_id: project.namespace, project_id: project, id: 'story-1' }
+
+          expect(assigns(:issue_json)).to be_nil
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to render_template(:show)
+        end
+
+        it 'returns JSON response with error messages' do
+          get :show, params: { namespace_id: project.namespace, project_id: project, id: 'story-1', format: :json }
 
-        expect(json_response).to eq(issue_json)
+          expect(response).to have_gitlab_http_status(:bad_request)
+          expect(json_response['errors']).to be_present
+        end
       end
 
       context 'when the JSON fetched from ZenTao contains HTML' do