=== modified file 'src/lightdm-gtk-greeter.c'
--- src/lightdm-gtk-greeter.c	2017-09-23 01:20:34 +0000
+++ src/lightdm-gtk-greeter.c	2017-09-24 15:25:01 +0000
@@ -2747,6 +2747,16 @@ main (int argc, char **argv)
     /* LP: #1024482 */
     g_setenv ("GDK_CORE_DEVICE_EVENTS", "1", TRUE);
 
+    #ifdef AT_SPI_COMMAND
+    /* Start AT-SPI before gtk initialization, so we know how to terminate it.  */
+    spawn_line_pid (AT_SPI_COMMAND, G_SPAWN_SEARCH_PATH, NULL);
+    #else
+    /* We do not know how to start AT-SPI. Prevent gtk3 from auto-starting it,
+       because otherwise the AT-SPI processes would remain during the user
+       session, preventing AT-SPI from working there.  */
+    g_setenv ("NO_AT_BRIDGE", "1", TRUE);
+    #endif
+
     /* Initialize i18n */
     setlocale (LC_ALL, "");
     bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);
@@ -2876,10 +2886,6 @@ main (int argc, char **argv)
         g_free (value);
     }
 
-    #ifdef AT_SPI_COMMAND
-    spawn_line_pid (AT_SPI_COMMAND, G_SPAWN_SEARCH_PATH, NULL);
-    #endif
-
     #ifdef INDICATOR_SERVICES_COMMAND
     spawn_line_pid (INDICATOR_SERVICES_COMMAND, G_SPAWN_SEARCH_PATH, NULL);
     #endif