diff -u b/menu_block.module b/menu_block.module
--- b/menu_block.module
+++ b/menu_block.module
@@ -119,5 +119,10 @@
     // `{{ label }}`. Therefore, we have to set both template variables for
     // this to work consistently.
-    $variables['configuration']['label'] = $variables['label'] = !empty($variables['configuration']['label_display']) ? $config_label : '';
+    $variables['label'] = !empty($variables['configuration']['label_display']) ? $config_label : '';
+  }
+  // Even if there is no $variables['content']['#menu_block_configuration']['label'] we would like to change the label.
+  // This happens for example when there are no menu items to render. But we still need te set the menu label 
+  if (isset($variables['label'])) {
+    $variables['configuration']['label'] = $variables['label'];
   }
 }