diff --git a/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py b/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py
index 5b656d0e5fd4..2b5eef630a6f 100644
--- a/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py
+++ b/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py
@@ -2,6 +2,9 @@
 # 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/.
 
+import sys
+import unittest
+
 from firefox_puppeteer import PuppeteerMixin
 from marionette_driver import Wait
 from marionette_harness import MarionetteTestCase
@@ -54,3 +57,25 @@ class TestBrowserWindowShortcuts(PuppeteerMixin, MarionetteTestCase):
             return selection_name == "input"
 
         Wait(self.marionette).until(has_input_selected)
+
+
+@unittest.skipIf(sys.platform == 'darwin',
+                 'Quit Shotcut not supported due to native menu of Mac OS')
+class TestBrowserQuitShortcut(PuppeteerMixin, MarionetteTestCase):
+
+    def test_quit_firefox_shortcut(self):
+        def quit_via_shortcut_callback():
+            if self.puppeteer.platform == 'win':
+                key = 'quitApplicationCmdWin2.accesskey'
+            else:
+                key = 'quitApplicationCmdUnix.key'
+
+            self.browser.send_shortcut(self.browser.localize_entity(key),
+                                       accel=True)
+
+        self.marionette.quit(in_app=True, callback=quit_via_shortcut_callback)
+        self.assertIsNone(self.marionette.session)
+
+    def tearDown(self):
+        self.marionette.start_session()
+        super(TestBrowserQuitShortcut, self).tearDown()
diff --git a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/windows.py b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/windows.py
index f81ba4b56869..7cf0e6946c4e 100644
--- a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/windows.py
+++ b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/windows.py
@@ -409,8 +409,7 @@ class BaseWindow(BaseLib):
             if kwargs[modifier] is True:
                 keys.append(keymap[modifier])
 
-        # Bug 1125209 - Only lower-case command keys should be sent
-        keys.append(command_key.lower())
+        keys.append(command_key)
 
         self.switch_to()