diff --git a/core/includes/module.inc b/core/includes/module.inc
index db1947d..a772436 100644
--- a/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -11,30 +11,26 @@
 /**
  * Loads all the modules that have been enabled in the system table.
  *
- * @param bool $bootstrap
+ * @param $bootstrap
  *   Whether to load only the reduced set of modules loaded in "bootstrap mode"
- *   for cached pages. See bootstrap.inc. Pass NULL to only check the current
- *   status without loading of modules.
- * @param bool $reset
- *   (optional) Internal use only. Whether to reset the internal statically
- *   cached flag of whether modules have been loaded. If TRUE, all modules are
- *   (re)loaded in the same call. Used by the testing framework to override and
- *   persist a limited module list for the duration of a unit test (in which no
- *   module system exists).
+ *   for cached pages. See bootstrap.inc.
  *
- * @return bool
- *   A Boolean indicating whether all modules have been loaded. This means all
- *   modules; the load status of bootstrap modules cannot be checked.
+ * @return
+ *   If $bootstrap is NULL, return a boolean indicating whether all modules
+ *   have been loaded.
  */
-function module_load_all($bootstrap = FALSE, $reset = FALSE) {
-  static $has_run = FALSE;
-
-  if ($reset) {
-    $has_run = FALSE;
+function module_load_all($bootstrap = FALSE) {
+  // Already loaded code cannot be unloaded, but new modules may be added within
+  // a request, which should be loaded as well.
+  // Use the advanced drupal_static() pattern, since this is called very often.
+  // @see theme()
+  static $drupal_static_fast;
+  if (!isset($drupal_static_fast)) {
+    $drupal_static_fast['has_run'] = &drupal_static(__FUNCTION__, FALSE);
   }
+  $has_run = &$drupal_static_fast['has_run'];
 
-  // Unless $boostrap is NULL, load the requested set of modules.
-  if (isset($bootstrap) && !$has_run) {
+  if (isset($bootstrap)) {
     $type = $bootstrap ? 'bootstrap' : 'module_enabled';
     foreach (module_list($type) as $module) {
       drupal_load('module', $module);
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index 048da36..00eb07f 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -796,9 +796,8 @@ protected function tearDown() {
     // Reset all static variables.
     drupal_static_reset();
 
-    // Reset module list and module load status.
+    // Reset module list.
     module_list_reset();
-    module_load_all(FALSE, TRUE);
 
     // Restore original in-memory configuration.
     $conf = $this->originalConf;