diff --git a/lib/carto/tree/variable.js b/lib/carto/tree/variable.js
index 2a3961e..103e423 100644
--- a/lib/carto/tree/variable.js
+++ b/lib/carto/tree/variable.js
@@ -9,7 +9,7 @@ tree.Variable.prototype = {
     eval: function(env) {
         var variable,
             v,
-            that = this;
+            that = this,
             name = this.name;
 
         if (this._css) return this._css;