diff --git a/openslides/core/static/css/app.css b/openslides/core/static/css/app.css
index 618941d4e..a51974ff6 100644
--- a/openslides/core/static/css/app.css
+++ b/openslides/core/static/css/app.css
@@ -87,6 +87,11 @@ img {
     color: #999;
 }
 
+#header div.unconnected {
+    border: 1px solid red;
+    position: fixed;
+    width: 100%;
+}
 #header a.headerlink {
     text-decoration: none;
 }
diff --git a/openslides/core/static/templates/index.html b/openslides/core/static/templates/index.html
index 1b0d7de86..3c3d52816 100644
--- a/openslides/core/static/templates/index.html
+++ b/openslides/core/static/templates/index.html
@@ -16,6 +16,7 @@
 
 <!-- Header -->
 <div id="header">
+  <div ng-hide="connected" class="unconnected"></div>
   <div class="containerOS">
     <!-- Logo -->
     <div class="title">