diff --git a/polyfills/url.js b/polyfills/url.js
index 076dd8b..d069271 100644
--- a/polyfills/url.js
+++ b/polyfills/url.js
@@ -380,7 +380,7 @@ function parse(self, url, parseQueryString, slashesDenoteHost) {
 function urlFileURLToPath(path) {
   if (typeof path === 'string')
     path = new Url().parse(path);
-  else if (!(url instanceof Url))
+  else if (!(path instanceof Url))
     throw new TypeError('The "path" argument must be of type string or an instance of URL. Received type ' + (typeof path) + String(path));
   if (path.protocol !== 'file:')
     throw new TypeError('The URL must be of scheme file');