diff --git a/src/Symfony/Component/Debug/DebugClassLoader.php b/src/Symfony/Component/Debug/DebugClassLoader.php
index 8c797744d7..95ccc8798e 100644
--- a/src/Symfony/Component/Debug/DebugClassLoader.php
+++ b/src/Symfony/Component/Debug/DebugClassLoader.php
@@ -147,7 +147,7 @@ class DebugClassLoader
         try {
             if ($this->isFinder) {
                 if ($file = $this->classLoader[0]->findFile($class)) {
-                    require $file;
+                    require_once $file;
                 }
             } else {
                 call_user_func($this->classLoader, $class);