diff --git a/lib/OpenLayers/Style.js b/lib/OpenLayers/Style.js
index 2595f25bcb..c04c2e717b 100644
--- a/lib/OpenLayers/Style.js
+++ b/lib/OpenLayers/Style.js
@@ -333,7 +333,7 @@ OpenLayers.Style = OpenLayers.Class({
      * rules - {Array(<OpenLayers.Rule>)}
      */
     addRules: function(rules) {
-        this.rules = this.rules.concat(rules);
+        Array.prototype.push.apply(this.rules, rules);
         this.propertyStyles = this.findPropertyStyles();
     },