https://github.com/mate-desktop/mate-session-manager/issues/189

Index: mate-session/gsm-manager.c
--- mate-session/gsm-manager.c.orig
+++ mate-session/gsm-manager.c
@@ -424,11 +424,10 @@ quit_request_completed_consolekit (GsmConsolekit *cons
 
         if (error != NULL) {
                 mdm_set_logout_action (fallback_action);
-        }
-
-        g_object_unref (consolekit);
-
-        gtk_main_quit ();
+        } else {
+                g_object_unref (consolekit);
+                gtk_main_quit ();
+	}
 }
 
 #ifdef HAVE_SYSTEMD
@@ -3018,7 +3017,7 @@ request_reboot_privileges_completed_consolekit (GsmCon
                         priv->logout_type = GSM_MANAGER_LOGOUT_REBOOT;
                 }
 
-                end_phase (manager);
+                gsm_manager_quit (manager);
         }
 }
 
@@ -3158,7 +3157,7 @@ request_shutdown_privileges_completed_consolekit (GsmC
                         priv->logout_type = GSM_MANAGER_LOGOUT_SHUTDOWN;
                 }
 
-                end_phase (manager);
+                gsm_manager_quit (manager);
         }
 }