diff -u b/core/includes/module.inc b/core/includes/module.inc
--- b/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -133,14 +133,15 @@
   }
 
   $key = $type . ':' . $module . ':' . $name;
-  if (!isset($files[$key])) {
-    if (function_exists('drupal_get_path')) {
-      $file = DRUPAL_ROOT . '/' . drupal_get_path('module', $module) . "/$name.$type";
-      if (is_file($file)) {
-        require_once $file;
-        $files[$key] = $file;
-        return $file;
-      }
+  if (isset($files[$key])) {
+    return $files[$key];
+  }
+  if (function_exists('drupal_get_path')) {
+    $file = DRUPAL_ROOT . '/' . drupal_get_path('module', $module) . "/$name.$type";
+    if (is_file($file)) {
+      require_once $file;
+      $files[$key] = $file;
+      return $file;
     }
   }
   return FALSE;
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
@@ -271,14 +271,15 @@
 
     $name = $name ?: $module;
     $key = $type . ':' . $module . ':' . $name;
-    if (!isset($this->includeFileKeys[$key])) {
-      if (isset($this->moduleList[$module])) {
-        $file = $this->root . '/' . $this->moduleList[$module]->getPath() . "/$name.$type";
-        if (is_file($file)) {
-          require_once $file;
-          $this->includeFileKeys[$key] = $file;
-          return $file;
-        }
+    if (isset($this->includeFileKeys[$key])) {
+      return $this->includeFileKeys[$key];
+    }
+    if (isset($this->moduleList[$module])) {
+      $file = $this->root . '/' . $this->moduleList[$module]->getPath() . "/$name.$type";
+      if (is_file($file)) {
+        require_once $file;
+        $this->includeFileKeys[$key] = $file;
+        return $file;
       }
     }
     return FALSE;