diff --git a/debian/postinst b/debian/postinst
index 026b12f..739fcd8 100644
--- a/debian/postinst
+++ b/debian/postinst
@@ -1,6 +1,6 @@
 #!/bin/sh
-
 set -e
+set -u
 
 case "$1" in
     configure)
diff --git a/debian/preinst b/debian/preinst
deleted file mode 100644
index cb117a0..0000000
--- a/debian/preinst
+++ /dev/null
@@ -1,13 +0,0 @@
-#!/bin/sh
-
-set -e
-
-case "$1" in
-    upgrade)
-        [ -f /usr/bin/startlxqt ] && update-alternatives --remove x-window-manager /usr/bin/startlxqt
-        ;;
-esac
-
-#DEBHELPER#
-
-exit 0
diff --git a/debian/prerm b/debian/prerm
index 55977eb..cdca015 100644
--- a/debian/prerm
+++ b/debian/prerm
@@ -1,9 +1,9 @@
 #!/bin/sh
-
 set -e
+set -u
 
 case "$1" in
-    remove)
+    remove|purge)
         update-alternatives --remove x-session-manager /usr/bin/startlxqt
         ;;
 esac