diff --git a/composer.json b/composer.json
index 39ff413e00..b200035f08 100644
--- a/composer.json
+++ b/composer.json
@@ -20,6 +20,7 @@
         "doctrine/common": "~2.4",
         "paragonie/random_compat": "~1.0",
         "symfony/polyfill-apcu": "~1.1",
+        "symfony/polyfill-mbstring": "~1.1",
         "twig/twig": "~1.23|~2.0",
         "psr/log": "~1.0"
     },
diff --git a/src/Symfony/Component/HttpFoundation/Tests/BinaryFileResponseTest.php b/src/Symfony/Component/HttpFoundation/Tests/BinaryFileResponseTest.php
index ac6c3288ae..4c055ff8a1 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/BinaryFileResponseTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/BinaryFileResponseTest.php
@@ -36,7 +36,13 @@ class BinaryFileResponseTest extends ResponseTestCase
 
     public function testConstructWithNonAsciiFilename()
     {
-        new BinaryFileResponse(__DIR__.'/Fixtures/föö.html', 200, array(), true, 'attachment');
+        touch(sys_get_temp_dir().'/fööö.html');
+
+        $response = new BinaryFileResponse(sys_get_temp_dir().'/fööö.html', 200, array(), true, 'attachment');
+
+        @unlink(sys_get_temp_dir().'/fööö.html');
+
+        $this->assertSame('fööö.html', $response->getFile()->getFilename());
     }
 
     /**
diff --git a/src/Symfony/Component/HttpFoundation/Tests/Fixtures/föö.html b/src/Symfony/Component/HttpFoundation/Tests/Fixtures/föö.html
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/src/Symfony/Component/HttpFoundation/composer.json b/src/Symfony/Component/HttpFoundation/composer.json
index 8fa1a00ec9..c9cbfd02aa 100644
--- a/src/Symfony/Component/HttpFoundation/composer.json
+++ b/src/Symfony/Component/HttpFoundation/composer.json
@@ -16,7 +16,8 @@
         }
     ],
     "require": {
-        "php": ">=5.3.3"
+        "php": ">=5.3.3",
+        "symfony/polyfill-mbstring": "~1.1"
     },
     "autoload": {
         "psr-0": { "Symfony\\Component\\HttpFoundation\\": "" },