diff --git a/core/lib/Drupal/Core/File/FileSystem.php b/core/lib/Drupal/Core/File/FileSystem.php
index d6f94ea..aedfdf6 100644
--- a/core/lib/Drupal/Core/File/FileSystem.php
+++ b/core/lib/Drupal/Core/File/FileSystem.php
@@ -301,7 +301,7 @@ public function validScheme($scheme) {
     if (!$scheme) {
       return FALSE;
     }
-    return class_exists($this->streamWrapperManager->getClass($scheme)) || in_array($scheme, stream_get_wrappers());
+    return class_exists($this->streamWrapperManager->getClass($scheme));
   }
 
 }
diff --git a/core/lib/Drupal/Core/StreamWrapper/StreamWrapperManager.php b/core/lib/Drupal/Core/StreamWrapper/StreamWrapperManager.php
index 7867b91..dc9f4b6 100644
--- a/core/lib/Drupal/Core/StreamWrapper/StreamWrapperManager.php
+++ b/core/lib/Drupal/Core/StreamWrapper/StreamWrapperManager.php
@@ -115,13 +115,6 @@ public function getClass($scheme) {
       return $this->info[$scheme]['class'];
     }
 
-    // Try to find it in wrappers.
-    foreach ($this->wrappers as $type => $wrappers) {
-      if (isset($this->wrappers[$type][$scheme])) {
-        return $this->wrappers[$type][$scheme]['class'];
-      }
-    }
-
     return FALSE;
   }
 
@@ -161,7 +154,7 @@ protected function getWrapper($scheme, $uri) {
   public function addStreamWrapper($service_id, $class, $scheme) {
     $this->info[$scheme] = array(
       'class' => $class,
-      'type' => method_exists($class, 'getType') ? $class::getType() : StreamWrapperInterface::ALL,
+      'type' => $class::getType(),
       'service_id' => $service_id,
     );
   }