diff --git a/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
index 5024e39..2bda4c7 100644
--- a/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -238,7 +238,7 @@ function seven_form_node_form_alter(&$form, FormStateInterface $form_state) {
  */
 function seven_preprocess_details(&$variables) {
   // Add the summary camel casing class on simpletest elements.
-  if( $variables['element']['summary']['#theme'] == 'simpletest_result_summary') {
+  if( isset($variables['element']['summary']['#theme']) && $variables['element']['summary']['#theme'] == 'simpletest_result_summary') {
     $variables['summary_attributes']['class'] = array('summary--camel-case');
   }