Index: gdm-3.31.91/data/Init.in
===================================================================
--- gdm-3.31.91.orig/data/Init.in	2019-02-21 20:44:14.000000000 +0100
+++ gdm-3.31.91/data/Init.in	2019-02-27 07:46:21.401932235 +0100
@@ -1,4 +1,9 @@
 #!/bin/sh
+
+if test -x /etc/X11/xdm/Xsetup; then
+	exec /etc/X11/xdm/Xsetup
+fi
+
 # Stolen from the debian kdm setup, aren't I sneaky
 # Plus a lot of fun stuff added
 #  -George
Index: gdm-3.31.91/data/PostSession.in
===================================================================
--- gdm-3.31.91.orig/data/PostSession.in	2018-10-12 23:05:26.000000000 +0200
+++ gdm-3.31.91/data/PostSession.in	2019-02-27 07:46:21.401932235 +0100
@@ -1,3 +1,7 @@
 #!/bin/sh
 
+if test -x /etc/X11/xdm/Xreset; then
+       exec /etc/X11/xdm/Xreset
+fi
+
 exit 0
Index: gdm-3.31.91/data/Xsession.in
===================================================================
--- gdm-3.31.91.orig/data/Xsession.in	2019-02-21 20:44:14.000000000 +0100
+++ gdm-3.31.91/data/Xsession.in	2019-02-27 07:46:21.401932235 +0100
@@ -1,4 +1,9 @@
 #!@XSESSION_SHELL@
+
+if test -x /etc/X11/xdm/Xsession; then
+       exec /etc/X11/xdm/Xsession $1 $GDM_LANG
+fi
+
 #
 # This is SORT OF LIKE an X session, but not quite.  You get a command as the
 # first argument (it could be multiple words, so run it with "eval").  As a
Index: gdm-3.31.91/data/PreSession.in
===================================================================
--- gdm-3.31.91.orig/data/PreSession.in	2018-10-12 23:05:26.000000000 +0200
+++ gdm-3.31.91/data/PreSession.in	2019-02-27 07:46:21.401932235 +0100
@@ -6,4 +6,8 @@
 #
 # Note that output goes into the .xsession-errors file for easy debugging
 #
+if test -x /etc/X11/xdm/Xstartup; then
+       exec /etc/X11/xdm/Xstartup
+fi
+
 PATH="@X_PATH@:$PATH"