--- a/browser/components/migration/tests/marionette/test_refresh_firefox.py
+++ b/browser/components/migration/tests/marionette/test_refresh_firefox.py
@@ -125,18 +125,26 @@ class TestFirefoxRefresh(MarionetteTestC
                   if (!expectedURLs.length) {
                     gBrowser.removeTabsProgressListener(this);
                     marionetteScriptFinished();
                   }
                 });
               }
             }
           });
+          let expectedTabs = new Set();
           for (let url of expectedURLs) {
-            gBrowser.addTab(url);
+            expectedTabs.add(gBrowser.addTab(url));
+          }
+          // Close any other tabs that might be open:
+          let allTabs = Array.from(gBrowser.tabs);
+          for (let tab of allTabs) {
+            if (!expectedTabs.has(tab)) {
+              gBrowser.removeTab(tab);
+            }
           }
         """, script_args=[self._expectedURLs])
 
     def checkPassword(self):
         loginInfo = self.marionette.execute_script("""
           let ary = Services.logins.findLogins({},
             "test.marionette.mozilla.com",
             "http://test.marionette.mozilla.com/some/form/",
@@ -270,18 +278,17 @@ class TestFirefoxRefresh(MarionetteTestC
           window.addEventListener("SSWindowStateReady", function testSSPostReset() {
             window.removeEventListener("SSWindowStateReady", testSSPostReset, false);
             Promise.all(gBrowser.browsers.map(b => TabStateFlusher.flush(b))).then(function() {
               marionetteScriptFinished([... gBrowser.browsers].map(b => b.currentURI && b.currentURI.spec));
             });
           }, false);
           mm.loadFrameScript("data:application/javascript,(" + fs.toString() + ")()", true);
         """)
-        self.assertSequenceEqual(tabURIs, ["about:blank"] + self._expectedURLs)
-        pass
+        self.assertSequenceEqual(tabURIs, self._expectedURLs)
 
     def checkProfile(self, hasMigrated=False):
         self.checkPassword()
         self.checkBookmark()
         self.checkHistory()
         self.checkFormHistory()
         self.checkCookie()
         if hasMigrated: