diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index 91bd7adb5b02..d52c31f3b403 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -2400,9 +2400,11 @@ function URLBarSetURI(aURI) {
 }
 
 function losslessDecodeURI(aURI) {
-  var value = aURI.spec;
   if (aURI.schemeIs("moz-action"))
     throw new Error("losslessDecodeURI should never get a moz-action URI");
+
+  var value = aURI.spec;
+
   // Try to decode as UTF-8 if there's no encoding sequence that we would break.
   if (!/%25(?:3B|2F|3F|3A|40|26|3D|2B|24|2C|23)/i.test(value))
     try {