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 8a6c2e5677666..b1a19f0ea1924 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
@@ -224,7 +224,7 @@
         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);
             };