diff --git a/CHANGELOG b/CHANGELOG
index dd42f09..ac6289a 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Add line numbers to failures when unit testing in Firefox.  Closes #9231.  [John Resig]
+
 * Fix Function#argumentNames for Opera and IE.  [Thomas Fuchs]
 
 * Add Object.isString, Object.isNumber, and Object.isUndefined, and clean up the source to make use of Object.isXXX where possible.  [sam]
diff --git a/test/lib/unittest.js b/test/lib/unittest.js
index 73883ae..da849e1 100644
--- a/test/lib/unittest.js
+++ b/test/lib/unittest.js
@@ -277,7 +277,15 @@ Test.Unit.Assertions.prototype = {
   },
   fail: function(message) {
     this.failures++;
-    this.messages.push("Failure: " + message);
+
+    var line = "";
+    try {
+      throw new Error("stack");
+    } catch(e){
+      line = (/\.html:(\d+)/.exec(e.stack || '') || ['',''])[1];
+    }
+
+    this.messages.push("Failure: " + message + (line ? " Line #" + line : ""));
   },
   info: function(message) {
     this.messages.push("Info: " + message);