diff --git a/lib/less/node/url.js b/lib/less/node/url.js
index 2bbfa668..4b32866d 100644
--- a/lib/less/node/url.js
+++ b/lib/less/node/url.js
@@ -5,6 +5,6 @@ tree.URL = function URL(val) {
 };
 tree.URL.prototype = {
     toCSS: function () {
-        return "url(" + (this.value.toCSS ? this.value.toCSS() : this.value + ")");
+        return "url(" + (this.value.toCSS ? this.value.toCSS() : this.value) + ")";
     }
 };