diff --git a/debian/changelog b/debian/changelog
index f13a1c6..7f710ee 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+raspi-config (20200109) UNRELEASED; urgency=medium
+
+  * Handle cases where SUDO_USER is unset
+
+ -- Serge Schneider <serge@raspberrypi.org>  Thu, 09 Jan 2020 14:38:50 +0000
+
 raspi-config (20191210) buster; urgency=medium
 
   * Fix postrm script
diff --git a/raspi-config b/raspi-config
index 4082109..cb5a52f 100755
--- a/raspi-config
+++ b/raspi-config
@@ -8,6 +8,8 @@ ASK_TO_REBOOT=0
 BLACKLIST=/etc/modprobe.d/raspi-blacklist.conf
 CONFIG=/boot/config.txt
 
+USER=${SUDO_USER:-$(who -m | awk '{ print $1 }')}
+
 is_pi () {
   ARCH=$(dpkg --print-architecture)
   if [ "$ARCH" = "armhf" ] ; then
@@ -443,8 +445,8 @@ do_pixdub() {
 }
 
 do_change_pass() {
-  whiptail --msgbox "You will now be asked to enter a new password for the $SUDO_USER user" 20 60 1
-  passwd $SUDO_USER &&
+  whiptail --msgbox "You will now be asked to enter a new password for the $USER user" 20 60 1
+  passwd $USER &&
   whiptail --msgbox "Password changed successfully" 20 60 1
 }
 
@@ -1105,9 +1107,9 @@ do_boot_behaviour() {
   if [ "$INTERACTIVE" = True ]; then
     BOOTOPT=$(whiptail --title "Raspberry Pi Software Configuration Tool (raspi-config)" --menu "Boot Options" $WT_HEIGHT $WT_WIDTH $WT_MENU_HEIGHT \
       "B1 Console" "Text console, requiring user to login" \
-      "B2 Console Autologin" "Text console, automatically logged in as '$SUDO_USER' user" \
+      "B2 Console Autologin" "Text console, automatically logged in as '$USER' user" \
       "B3 Desktop" "Desktop GUI, requiring user to login" \
-      "B4 Desktop Autologin" "Desktop GUI, automatically logged in as '$SUDO_USER' user" \
+      "B4 Desktop Autologin" "Desktop GUI, automatically logged in as '$USER' user" \
       3>&1 1>&2 2>&3)
   else
     BOOTOPT=$1
@@ -1126,7 +1128,7 @@ do_boot_behaviour() {
         cat > /etc/systemd/system/getty@tty1.service.d/autologin.conf << EOF
 [Service]
 ExecStart=
-ExecStart=-/sbin/agetty --autologin $SUDO_USER --noclear %I \$TERM
+ExecStart=-/sbin/agetty --autologin $USER --noclear %I \$TERM
 EOF
         ;;
       B3*)
@@ -1148,9 +1150,9 @@ EOF
           cat > /etc/systemd/system/getty@tty1.service.d/autologin.conf << EOF
 [Service]
 ExecStart=
-ExecStart=-/sbin/agetty --autologin $SUDO_USER --noclear %I \$TERM
+ExecStart=-/sbin/agetty --autologin $USER --noclear %I \$TERM
 EOF
-          sed /etc/lightdm/lightdm.conf -i -e "s/^\(#\|\)autologin-user=.*/autologin-user=$SUDO_USER/"
+          sed /etc/lightdm/lightdm.conf -i -e "s/^\(#\|\)autologin-user=.*/autologin-user=$USER/"
           disable_raspi_config_at_boot
         else
           whiptail --msgbox "Do 'sudo apt-get install lightdm' to allow configuration of boot to desktop" 20 60 2
@@ -2275,10 +2277,15 @@ do_network_menu() {
 if [ "$INTERACTIVE" = True ]; then
   [ -e $CONFIG ] || touch $CONFIG
   calc_wt_size
+  while [ "$USER" = "root" ] || [ -z "$USER" ]; do
+    if ! USER=$(whiptail --inputbox "raspi-config could not determine the default user.\\n\\nWhat user should these settings apply to?" 20 60 pi 3>&1 1>&2 2>&3); then
+      return 0
+    fi
+  done
   while true; do
     if is_pi ; then
       FUN=$(whiptail --title "Raspberry Pi Software Configuration Tool (raspi-config)" --backtitle "$(cat /proc/device-tree/model)" --menu "Setup Options" $WT_HEIGHT $WT_WIDTH $WT_MENU_HEIGHT --cancel-button Finish --ok-button Select \
-        "1 Change User Password" "Change password for the current user" \
+        "1 Change User Password" "Change password for the '$USER' user" \
         "2 Network Options" "Configure network settings" \
         "3 Boot Options" "Configure options for start-up" \
         "4 Localisation Options" "Set up language and regional settings to match your location" \
@@ -2290,7 +2297,7 @@ if [ "$INTERACTIVE" = True ]; then
         3>&1 1>&2 2>&3)
     else
       FUN=$(whiptail --title "Raspberry Pi Software Configuration Tool (raspi-config)" --menu "Setup Options" $WT_HEIGHT $WT_WIDTH $WT_MENU_HEIGHT --cancel-button Finish --ok-button Select \
-        "1 Change User Password" "Change password for the current user" \
+        "1 Change User Password" "Change password for the '$USER' user" \
         "2 Network Options" "Configure network settings" \
         "3 Boot Options" "Configure options for start-up" \
         "4 Localisation Options" "Set up language and regional settings to match your location" \