diff --git a/core/lib/Drupal/Core/StreamWrapper/ModuleStream.php b/core/lib/Drupal/Core/StreamWrapper/ModuleStream.php
index efd81a0..b56f183 100644
--- a/core/lib/Drupal/Core/StreamWrapper/ModuleStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/ModuleStream.php
@@ -21,8 +21,8 @@ public function getOwnerName($uri = NULL) {
       return $name;
     }
     else {
-      // The module does not exist or is disabled.
-      throw new \InvalidArgumentException(sprintf('Module %s does not exist or is disabled', $name));
+      // The module does not exist or is not enabled.
+      throw new \InvalidArgumentException(sprintf('Module %s does not exist or is not enabled', $name));
     }
   }
 
diff --git a/core/lib/Drupal/Core/StreamWrapper/SystemStream.php b/core/lib/Drupal/Core/StreamWrapper/SystemStream.php
index 4460ee6..019cf88 100644
--- a/core/lib/Drupal/Core/StreamWrapper/SystemStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/SystemStream.php
@@ -53,7 +53,7 @@ public function getTarget($uri = NULL) {
       return trim($target, '/');
     }
     else {
-      throw new \InvalidArgumentException(sprintf('Target %s does not exist', $uri));
+      throw new \InvalidArgumentException(sprintf('File %s does not exist', $uri));
     }
   }
 
@@ -85,6 +85,6 @@ public function getExternalUrl($uri = NULL) {
       $path = rtrim(UrlHelper::encodePath(str_replace('\\', '/', $path)), '/');
     }
 
-    return \Drupal::request()->getUri() . $dir . $path;
+    return \Drupal::request()->getUriForPath('/' . $dir . $path);
   }
 }
diff --git a/core/modules/system/src/Tests/File/SystemStreamUnitTest.php b/core/modules/system/src/Tests/File/SystemStreamTest.php
similarity index 98%
rename from core/modules/system/src/Tests/File/SystemStreamUnitTest.php
rename to core/modules/system/src/Tests/File/SystemStreamTest.php
index be33a14..75d4be9 100644
--- a/core/modules/system/src/Tests/File/SystemStreamUnitTest.php
+++ b/core/modules/system/src/Tests/File/SystemStreamTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\system\Tests\File\SystemStreamUnitTest.
+ * Contains \Drupal\system\Tests\File\SystemStreamTest.
  */
 
 namespace Drupal\system\Tests\File;
@@ -16,7 +16,7 @@
  *
  * @group system
  */
-class SystemStreamUnitTest extends KernelTestBase {
+class SystemStreamTest extends KernelTestBase {
 
   /**
    * Modules to enable.
@@ -404,7 +404,10 @@ private function runTestOnInstanceMethod($instance, $method, array $data) {
         }
       }
       else {
-        $this->assertEqual($instance->$method($uri), $info[0], $info[1]);
+        if (!$this->assertEqual($instance->$method($uri), $info[0], $info[1])) {
+          debug($instance->$method($uri), get_class($instance) . "::$method('$uri')");
+          debug($info[0], 'expected');
+        }
       }
     }
   }