diff --git a/lib/techs/css-base.js b/lib/techs/css-base.js
index <HASH>..<HASH> 100644
--- a/lib/techs/css-base.js
+++ b/lib/techs/css-base.js
@@ -22,7 +22,7 @@ exports.Tech = INHERIT(base.Tech, {
                 url = url.substring(0, i);
             }
 
-            if (this.tech.opts.freeze && FREEZE.isFreezableUrl(url)) {
+            if (this.tech.opts.freeze && this.isFreezableUrl(url)) {
                 url = FREEZE.processPath(url);
             }
 
@@ -31,6 +31,10 @@ exports.Tech = INHERIT(base.Tech, {
             url = (resolved == url ? PATH.relative(PATH.dirname(path), url) : resolved) + postUrl;
 
             return JSON.stringify(url);
+        },
+
+        isFreezableUrl: function(url) {
+            return FREEZE.isFreezableUrl(url);
         }
 
     })
Add flexibility to freeze

So I can extend tech with my custom extensions in this way

my-tech.js
```js
isFreezableUrl: function(url) {
  return this.__base(url) || myRe.test(url)
}
```