--- a/src/lightdm.c
+++ b/src/lightdm.c
@@ -779,7 +779,7 @@
     if (!config_has_key (config_get_instance (), "Seat:*", "allow-user-switching"))
         config_set_boolean (config_get_instance (), "Seat:*", "allow-user-switching", TRUE);
     if (!config_has_key (config_get_instance (), "Seat:*", "allow-guest"))
-        config_set_boolean (config_get_instance (), "Seat:*", "allow-guest", TRUE);
+        config_set_boolean (config_get_instance (), "Seat:*", "allow-guest", FALSE);
     if (!config_has_key (config_get_instance (), "Seat:*", "greeter-allow-guest"))
         config_set_boolean (config_get_instance (), "Seat:*", "greeter-allow-guest", TRUE);
     if (!config_has_key (config_get_instance (), "Seat:*", "greeter-show-remote-login"))
--- a/data/lightdm.conf
+++ b/data/lightdm.conf
@@ -112,7 +112,7 @@
 #greeter-show-remote-login=true
 #user-session=default
 #allow-user-switching=true
-#allow-guest=true
+#allow-guest=false
 #guest-session=
 #session-wrapper=lightdm-session
 #greeter-wrapper=