diff --git a/classes/autoptimizeStyles.php b/classes/autoptimizeStyles.php
index d2183a49..dc8e9e06 100644
--- a/classes/autoptimizeStyles.php
+++ b/classes/autoptimizeStyles.php
@@ -545,7 +545,7 @@ public function getcontent() {
                 if($this->defer == true) {
                     
                     // Filter to modify the onload attribute - passes value and the stylesheet url
-                    $preloadOnLoad = apply_filters('autoptimize_filter_css_preload_onload', "this.rel=\'stylesheet\'", $url);
+                    $preloadOnLoad = apply_filters('autoptimize_filter_css_preload_onload', "this.rel='stylesheet'", $url);
                     
                     $preloadCssBlock .= '<link rel="preload" as="style" media="'.$media.'" href="'.$url.'" onload="'.$preloadOnLoad.'" />';
                     $noScriptCssBlock .= '<link type="text/css" media="'.$media.'" href="'.$url.'" rel="stylesheet" />';