diff --git a/src/Symfony/Bundle/WebProfilerBundle/Resources/views/Profiler/base_js.html.twig b/src/Symfony/Bundle/WebProfilerBundle/Resources/views/Profiler/base_js.html.twig
index 23e05030c5..a1b9c4ffd9 100644
--- a/src/Symfony/Bundle/WebProfilerBundle/Resources/views/Profiler/base_js.html.twig
+++ b/src/Symfony/Bundle/WebProfilerBundle/Resources/views/Profiler/base_js.html.twig
@@ -209,7 +209,7 @@
         var addEventListener;
 
         var el = document.createElement('div');
-        if (!'addEventListener' in el) {
+        if (!('addEventListener' in el)) {
             addEventListener = function (element, eventName, callback) {
                 element.attachEvent('on' + eventName, callback);
             };