diff --git a/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php b/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php
index fbd0a4fa4d..e8ca4ac940 100644
--- a/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php
+++ b/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php
@@ -30,17 +30,17 @@ class ClassExistsMock
 
     public static function class_exists($name, $autoload = true)
     {
-        return (bool) (self::$classes[ltrim($name, '\\')] ?? class_exists($name, $autoload));
+        return (bool) (self::$classes[ltrim($name, '\\')] ?? \class_exists($name, $autoload));
     }
 
     public static function interface_exists($name, $autoload = true)
     {
-        return (bool) (self::$classes[ltrim($name, '\\')] ?? interface_exists($name, $autoload));
+        return (bool) (self::$classes[ltrim($name, '\\')] ?? \interface_exists($name, $autoload));
     }
 
     public static function trait_exists($name, $autoload = true)
     {
-        return (bool) (self::$classes[ltrim($name, '\\')] ?? trait_exists($name, $autoload));
+        return (bool) (self::$classes[ltrim($name, '\\')] ?? \trait_exists($name, $autoload));
     }
 
     public static function register($class)