diff --git a/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
index 4336eced01..e60c2f7df7 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
@@ -391,7 +391,7 @@ class XmlFileLoader extends FileLoader
                     $arguments[$key] = $arg->nodeValue;
                     break;
                 case 'constant':
-                    $arguments[$key] = constant($arg->nodeValue);
+                    $arguments[$key] = constant(trim($arg->nodeValue));
                     break;
                 default:
                     $arguments[$key] = XmlUtils::phpize($arg->nodeValue);