diff --git a/src/Symfony/Bundle/SecurityBundle/composer.json b/src/Symfony/Bundle/SecurityBundle/composer.json
index 8e4bb9d0a2..d158443896 100644
--- a/src/Symfony/Bundle/SecurityBundle/composer.json
+++ b/src/Symfony/Bundle/SecurityBundle/composer.json
@@ -46,7 +46,7 @@
         "twig/twig": "~1.34|~2.4"
     },
     "conflict": {
-        "symfony/security": "4.1.0-beta1,4.1.0-beta2",
+        "symfony/security": "4.1.0-beta1|4.1.0-beta2",
         "symfony/var-dumper": "<3.3",
         "symfony/event-dispatcher": "<3.4",
         "symfony/framework-bundle": "<3.4",
diff --git a/src/Symfony/Component/HttpFoundation/File/MimeType/MimeTypeGuesser.php b/src/Symfony/Component/HttpFoundation/File/MimeType/MimeTypeGuesser.php
index e3ef45ef67..d78c760682 100644
--- a/src/Symfony/Component/HttpFoundation/File/MimeType/MimeTypeGuesser.php
+++ b/src/Symfony/Component/HttpFoundation/File/MimeType/MimeTypeGuesser.php
@@ -80,13 +80,8 @@ class MimeTypeGuesser implements MimeTypeGuesserInterface
      */
     private function __construct()
     {
-        if (FileBinaryMimeTypeGuesser::isSupported()) {
-            $this->register(new FileBinaryMimeTypeGuesser());
-        }
-
-        if (FileinfoMimeTypeGuesser::isSupported()) {
-            $this->register(new FileinfoMimeTypeGuesser());
-        }
+        $this->register(new FileBinaryMimeTypeGuesser());
+        $this->register(new FileinfoMimeTypeGuesser());
     }
 
     /**
@@ -125,18 +120,14 @@ class MimeTypeGuesser implements MimeTypeGuesserInterface
             throw new AccessDeniedException($path);
         }
 
-        if (!$this->guessers) {
-            $msg = 'Unable to guess the mime type as no guessers are available';
-            if (!FileinfoMimeTypeGuesser::isSupported()) {
-                $msg .= ' (Did you enable the php_fileinfo extension?)';
-            }
-            throw new \LogicException($msg);
-        }
-
         foreach ($this->guessers as $guesser) {
             if (null !== $mimeType = $guesser->guess($path)) {
                 return $mimeType;
             }
         }
+
+        if (2 === \count($this->guessers) && !FileBinaryMimeTypeGuesser::isSupported() && !FileinfoMimeTypeGuesser::isSupported()) {
+            throw new \LogicException('Unable to guess the mime type as no guessers are available (Did you enable the php_fileinfo extension?)');
+        }
     }
 }