diff --git a/core/includes/file.inc b/core/includes/file.inc
index c09743e..87f6689 100644
--- a/core/includes/file.inc
+++ b/core/includes/file.inc
@@ -199,9 +199,12 @@
  * @see hook_stream_wrappers_alter()
  */
 function file_get_stream_wrappers($filter = STREAM_WRAPPERS_ALL) {
-  $wrappers_storage = &drupal_static(__FUNCTION__);
+  $wrappers_storage = &drupal_static(__FUNCTION__, array());
 
-  if (!isset($wrappers_storage)) {
+  if (empty($wrappers_storage)) {
+    // Initialize $wrappers_storage, so that we are not calling this method
+    // repeatedly if no stream wrappers exist.
+    $wrappers_storage[STREAM_WRAPPERS_ALL] = array();
     $wrappers = array();
     if (\Drupal::hasService('module_handler')) {
       $wrappers = \Drupal::moduleHandler()->invokeAll('stream_wrappers');
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
index 64b55cb..d10ce9f 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
@@ -453,16 +453,10 @@ protected function unregisterStreamWrapper($scheme, $type) {
     unset($this->streamWrappers[$scheme]);
     // @todo Revamp Drupal's stream wrapper API for D8.
     // @see https://drupal.org/node/2028109
-    $wrappers = &drupal_static('file_get_stream_wrappers');
-    // If no module implementing hook_stream_wrappers() is enabled and a call to
-    // drupal_static_reset() is followed by a call to file_get_stream_wrappers(),
-    // then its static variable will be NULL, in which case no further action is
-    // required.
-    if (isset($wrappers)) {
-      foreach ($wrappers as $filter => $schemes) {
-        if (is_int($filter) && (($filter & $type) == $filter)) {
-          unset($wrappers[$filter][$scheme]);
-        }
+    $wrappers = &drupal_static('file_get_stream_wrappers', array());
+    foreach ($wrappers as $filter => $schemes) {
+      if (is_int($filter) && (($filter & $type) == $filter)) {
+        unset($wrappers[$filter][$scheme]);
       }
     }
   }