diff --git a/testing/marionette/components/marionette.js b/testing/marionette/components/marionette.js
index d0a7a184a1b7..a5bf353b2445 100644
--- a/testing/marionette/components/marionette.js
+++ b/testing/marionette/components/marionette.js
@@ -195,30 +195,27 @@ MarionetteComponent.prototype.observe = function(subject, topic, data) {
   this.logger.debug(`Received observer notification "${topic}"`);
 
   switch (topic) {
+    case "profile-after-change":
+      Services.obs.addObserver(this, "command-line-startup");
+      Services.obs.addObserver(this, "sessionstore-windows-restored");
+
+      prefs.readFromEnvironment(ENV_PRESERVE_PREFS);
+      break;
+
+    // In safe mode the command line handlers are getting parsed after the
+    // safe mode dialog has been closed. To allow Marionette to start
+    // earlier, use the CLI startup observer notification for
+    // special-cased handlers, which gets fired before the dialog appears.
     case "command-line-startup":
       Services.obs.removeObserver(this, topic);
       this.handle(subject);
 
-    case "profile-after-change":
-      // Using sessionstore-windows-restored as the xpcom category doesn't
-      // seem to work, so we wait for that by adding an observer here.
-      Services.obs.addObserver(this, "sessionstore-windows-restored");
-
-      // In safe mode the command line handlers are getting parsed after the
-      // safe mode dialog has been closed. To allow Marionette to start
-      // earlier, register the CLI startup observer notification for
-      // special-cased handlers, which gets fired before the dialog appears.
-      Services.obs.addObserver(this, "command-line-startup");
-
-      prefs.readFromEnvironment(ENV_PRESERVE_PREFS);
-
-      if (this.enabled) {
-        // We want to suppress the modal dialog that's shown
-        // when starting up in safe-mode to enable testing.
-        if (Services.appinfo.inSafeMode) {
-          Services.obs.addObserver(this, "domwindowopened");
-        }
+      // We want to suppress the modal dialog that's shown
+      // when starting up in safe-mode to enable testing.
+      if (this.enabled && Services.appinfo.inSafeMode) {
+        Services.obs.addObserver(this, "domwindowopened");
       }
+
       break;
 
     case "domwindowclosed":
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py b/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py
index f9bc072f3281..f6e5e8dff1fa 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_quit_restart.py
@@ -2,6 +2,8 @@
 # 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 unittest
+
 from marionette_driver import errors
 
 from marionette_harness import MarionetteTestCase, skip
@@ -88,6 +90,14 @@ class TestQuitRestart(MarionetteTestCase):
 
         MarionetteTestCase.tearDown(self)
 
+    @property
+    def is_safe_mode(self):
+        with self.marionette.using_context("chrome"):
+            return self.marionette.execute_script("""
+              Cu.import("resource://gre/modules/Services.jsm");
+              return Services.appinfo.inSafeMode;
+            """)
+
     def shutdown(self, restart=False):
         self.marionette.set_context("chrome")
         self.marionette.execute_script("""
@@ -187,6 +197,32 @@ class TestQuitRestart(MarionetteTestCase):
         self.assertNotEqual(self.marionette.get_pref("startup.homepage_welcome_url"),
                             "about:")
 
+    def test_in_app_restart_safe_mode(self):
+        if self.marionette.session_capabilities["moz:headless"]:
+            raise unittest.SkipTest("Bug 1390848 - Hang of Marionette client after the restart.")
+
+        def restart_in_safe_mode():
+            with self.marionette.using_context("chrome"):
+                self.marionette.execute_script("""
+                  Components.utils.import("resource://gre/modules/Services.jsm");
+
+                  let cancelQuit = Cc["@mozilla.org/supports-PRBool;1"]
+                                     .createInstance(Ci.nsISupportsPRBool);
+                  Services.obs.notifyObservers(cancelQuit,
+                      "quit-application-requested", null);
+
+                  if (!cancelQuit.data) {
+                    Services.startup.restartInSafeMode(Ci.nsIAppStartup.eAttemptQuit);
+                  }
+                """)
+
+        try:
+            self.assertFalse(self.is_safe_mode, "Safe Mode is unexpectedly enabled")
+            self.marionette.restart(in_app=True, callback=restart_in_safe_mode)
+            self.assertTrue(self.is_safe_mode, "Safe Mode is not enabled")
+        finally:
+            self.marionette.quit(clean=True)
+
     def test_in_app_restart_with_callback_no_shutdown(self):
         try:
             timeout_startup = self.marionette.DEFAULT_STARTUP_TIMEOUT