--- a/services/sync/tps/extensions/tps/resource/modules/tabs.jsm
+++ b/services/sync/tps/extensions/tps/resource/modules/tabs.jsm
@@ -24,20 +24,20 @@ var BrowserTabs = {
    * @return nothing
    */
   Add(uri, fn) {
     // Open the uri in a new tab in the current browser window, and calls
     // the callback fn from the tab's onload handler.
     let wm = Cc["@mozilla.org/appshell/window-mediator;1"]
                .getService(Ci.nsIWindowMediator);
     let mainWindow = wm.getMostRecentWindow("navigator:browser");
-    let newtab = mainWindow.getBrowser().addTab(uri);
-    mainWindow.getBrowser().selectedTab = newtab;
-    let win = mainWindow.getBrowser().getBrowserForTab(newtab);
-    win.addEventListener("load", function() { fn.call(); }, true);
+    let browser = mainWindow.getBrowser();
+    browser.addEventListener("load", fn, { once: true });
+    let newtab = browser.addTab(uri);
+    browser.selectedTab = newtab;
   },
 
   /**
    * Find
    *
    * Finds the specified uri and title in Weave's list of remote tabs
    * for the specified profile.
    *