diff --git a/lib/less/node/keyword.js b/lib/less/node/keyword.js
index 6d1df5e3..d7602cfd 100644
--- a/lib/less/node/keyword.js
+++ b/lib/less/node/keyword.js
@@ -1,6 +1,7 @@
 if (typeof(window) === 'undefined') { var tree = require(require('path').join(__dirname, '..', '..', 'less', 'tree')); }
 
 tree.Keyword = function Keyword(value) { this.value = value };
-tree.Keyword.prototype.toCSS = function () {
-    return this.value;
+tree.Keyword.prototype = {
+    eval: function () { return this },
+    toCSS: function () { return this.value }
 };