--- a/browser/base/content/test/browser_tabopen_reflows.js
+++ b/browser/base/content/test/browser_tabopen_reflows.js
@@ -33,18 +33,17 @@ const EXPECTED_REFLOWS = [
     "GroupItem_getContentBounds@chrome://browser/content/tabview.js|" +
     "GroupItem_shouldStack@chrome://browser/content/tabview.js|" +
     "GroupItem_arrange@chrome://browser/content/tabview.js|" +
     "GroupItem_add@chrome://browser/content/tabview.js|" +
     "GroupItems_newTab@chrome://browser/content/tabview.js|" +
     "TabItem__reconnect@chrome://browser/content/tabview.js|" +
     "TabItem@chrome://browser/content/tabview.js|" +
     "TabItems_link@chrome://browser/content/tabview.js|" +
-    "@chrome://browser/content/tabview.js|" +
-    "addTab@chrome://browser/content/tabbrowser.xml|",
+    "@chrome://browser/content/tabview.js|",
 
   // SessionStore.getWindowDimensions()
   "ssi_getWindowDimension@resource:///modules/sessionstore/SessionStore.jsm|" +
     "@resource:///modules/sessionstore/SessionStore.jsm|" +
     "ssi_updateWindowFeatures@resource:///modules/sessionstore/SessionStore.jsm|" +
     "ssi_collectWindowData@resource:///modules/sessionstore/SessionStore.jsm|",
 
   // tabPreviews.capture()
@@ -83,31 +82,32 @@ function test() {
 }
 
 let observer = {
   reflow: function (start, end) {
     // Gather information about the current code path.
     let path = (new Error().stack).split("\n").slice(1).map(line => {
       return line.replace(/:\d+$/, "");
     }).join("|");
+    let pathWithLineNumbers = (new Error().stack).split("\n").slice(1).join("|");
 
     // Stack trace is empty. Reflow was triggered by native code.
     if (path === "") {
       return;
     }
 
     // Check if this is an expected reflow.
     for (let stack of EXPECTED_REFLOWS) {
       if (path.startsWith(stack)) {
         ok(true, "expected uninterruptible reflow '" + stack + "'");
         return;
       }
     }
 
-    ok(false, "unexpected uninterruptible reflow '" + path + "'");
+    ok(false, "unexpected uninterruptible reflow '" + pathWithLineNumbers + "'");
   },
 
   reflowInterruptible: function (start, end) {
     // We're not interested in interruptible reflows.
   },
 
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIReflowObserver,
                                          Ci.nsISupportsWeakReference])