diff -u b/core/lib/Drupal/Core/Extension/ModuleHandler.php b/core/lib/Drupal/Core/Extension/ModuleHandler.php
--- b/core/lib/Drupal/Core/Extension/ModuleHandler.php
+++ b/core/lib/Drupal/Core/Extension/ModuleHandler.php
@@ -281,6 +281,9 @@
         $this->includeFileKeys[$key] = $file;
         return $file;
       }
+      else {
+        $this->includeFileKeys[$key] = FALSE;
+      }
     }
     return FALSE;
   }