--- a/toolkit/components/telemetry/tests/marionette/tests/client/test_main_tab_scalars.py
+++ b/toolkit/components/telemetry/tests/marionette/tests/client/test_main_tab_scalars.py
@@ -1,27 +1,36 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+from marionette_driver.wait import Wait
+
 from telemetry_harness.testcase import TelemetryTestCase
 
 
 class TestMainTabScalars(TelemetryTestCase):
 
     def test_main_tab_scalars(self):
+        wait = Wait(self.marionette, 10)
+
         with self.marionette.using_context(self.marionette.CONTEXT_CHROME):
             tab1 = self.browser.tabbar.selected_tab
             tab2 = self.browser.tabbar.open_tab()
+            wait.until(lambda m: len(self.browser.tabbar.tabs) == 2)
             self.browser.tabbar.switch_to(tab2)
             tab3 = self.browser.tabbar.open_tab()
+            wait.until(lambda m: len(self.browser.tabbar.tabs) == 3)
             self.browser.tabbar.switch_to(tab3)
             self.browser.tabbar.close_tab(tab3, force=True)
+            wait.until(lambda m: len(self.browser.tabbar.tabs) == 2)
             self.browser.tabbar.close_tab(tab2, force=True)
+            wait.until(lambda m: len(self.browser.tabbar.tabs) == 1)
             self.browser.tabbar.switch_to(tab1)
         self.restart_browser()
-        ping = self.wait_for_ping()
+        ping = self.wait_for_ping(lambda p: p['type'] == 'main'
+                                  and p['payload']['info']['reason'] == 'shutdown')
         assert ping['type'] == 'main'
         assert ping['clientId'] == self.client_id
         scalars = ping['payload']['processes']['parent']['scalars']
         assert scalars['browser.engagement.max_concurrent_tab_count'] == 3
         assert scalars['browser.engagement.tab_open_event_count'] == 2
         assert scalars['browser.engagement.max_concurrent_window_count'] == 1