diff --git a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
index 001b827..e1fd670 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/DrupalUnitTestBase.php
@@ -179,6 +179,7 @@ protected function setUp() {
     // StreamWrapper APIs.
     // @todo Move StreamWrapper management into DrupalKernel.
     // @see https://drupal.org/node/2028109
+    $this->streamWrappers = array();
     // The public stream wrapper only depends on the file_public_path setting,
     // which is provided by UnitTestBase::setUp().
     $this->registerStreamWrapper('public', 'Drupal\Core\StreamWrapper\PublicStream');
@@ -200,7 +201,6 @@ protected function tearDown() {
     foreach ($this->streamWrappers as $scheme) {
       $this->unregisterStreamWrapper($scheme);
     }
-    $this->streamWrappers = array();
     parent::tearDown();
   }
 
@@ -427,15 +427,12 @@ protected function registerStreamWrapper($scheme, $class, $type = STREAM_WRAPPER
     }
     // @todo Revamp Drupal's stream wrapper API for D8.
     // @see https://drupal.org/node/2028109
-    // Add the stream wrapper to the file_get_stream_wrappers() static cache,
-    // only set the ALL type so that other types will be recalculated when
-    // requested.
     $wrappers = &drupal_static('file_get_stream_wrappers', array());
-    $wrappers[STREAM_WRAPPERS_ALL][$scheme] = array(
+    $wrappers[$scheme] = array(
       'type' => $type,
       'class' => $class,
     );
-    $wrappers[$type][$scheme] = $wrappers[STREAM_WRAPPERS_ALL][$scheme];
+    $wrappers[STREAM_WRAPPERS_ALL] = $wrappers;
   }
 
   /**
@@ -452,18 +449,9 @@ protected function unregisterStreamWrapper($scheme) {
     unset($this->streamWrappers[$scheme]);
     // @todo Revamp Drupal's stream wrapper API for D8.
     // @see https://drupal.org/node/2028109
-    // Remove the stream wrapper from all existing types.
     $wrappers = &drupal_static('file_get_stream_wrappers', array());
-    // @todo Some tests seem to reset the static cache to an explict
-    //   NULL, for example the module_uninstall() call in
-    //   \Drupal\field\Tests\FieldInfoTest::testInstanceDisabledEntityType().
-    if (is_array($wrappers)) {
-      foreach ($wrappers as &$schemes) {
-        if (isset($schemes[$scheme])) {
-          unset($schemes[$scheme]);
-        }
-      }
-    }
+    unset($wrappers[$scheme]);
+    unset($wrappers[STREAM_WRAPPERS_ALL][$scheme]);
   }
 
 }