diff --git a/manifest.json b/manifest.json
index 72df08b..698ab38 100644
--- a/manifest.json
+++ b/manifest.json
@@ -6,7 +6,7 @@
         "en": "Offer backup storage to a friend.",
         "fr": "Offrez un espace de stockage à un⋅e ami⋅e."
     },
-    "version": "1.1.10~ynh3",
+    "version": "1.1.10~ynh4",
     "url": "https://borgbackup.readthedocs.io",
     "license": "BSD-3-Clause",
     "maintainer": {
diff --git a/scripts/_common.sh b/scripts/_common.sh
index af3b210..3ae7714 100644
--- a/scripts/_common.sh
+++ b/scripts/_common.sh
@@ -26,7 +26,7 @@ ynh_export () {
     local ynh_arg=""
     for var in $@;
     do
-        ynh_arg=$(echo $var | awk '{print toupper($0)}')
+        ynh_arg=$(echo "$var" | awk '{print toupper($0)}')
         if [ "$var" == "path_url" ]; then
             ynh_arg="PATH"
         fi
@@ -43,7 +43,7 @@ ynh_save_args () {
         if [ "$var" == "path_url" ]; then
             setting_var="path"
         fi
-        ynh_app_setting_set $app $setting_var ${!var}
+        ynh_app_setting_set $app $setting_var "${!var}"
     done
 }
 
diff --git a/scripts/upgrade b/scripts/upgrade
index 5ab24b3..bb19d2c 100755
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -14,6 +14,7 @@ source /usr/share/yunohost/helpers
 #=================================================
 
 app=$YNH_APP_INSTANCE_NAME
+ssh_user=$(ynh_app_setting_get --app=$app --key=ssh_user)
 
 #=================================================
 # CHECK IF AN UPGRADE IS NEEDED
@@ -33,8 +34,21 @@ ynh_clean_setup () {
 # Exit if an error occurs during the execution of the script
 ynh_abort_if_errors
 
-# Replace backports with pip
-rm -f /etc/apt/sources.list.d/$app-stretch-backports.list
 
-install_borg_with_pip
-ynh_secure_remove /etc/yunohost/hooks.d/backup/17-data_home
+#=================================================
+# ENSURE DOWNWARD COMPATIBILITY
+#=================================================
+ynh_script_progression --message="Ensuring downward compatibility..."
+
+if [ -f "/etc/apt/sources.list.d/$app-stretch-backports.list" ]; then
+    rm -f /etc/apt/sources.list.d/$app-stretch-backports.list
+    install_borg_with_pip
+fi
+
+if [ -f "/etc/yunohost/hooks.d/backup/17-data_home" ]; then
+    ynh_secure_remove /etc/yunohost/hooks.d/backup/17-data_home
+fi
+
+if echo "$ssh_user" | grep -v ' '; then
+    ynh_app_setting_set --app=$app --key=ssh_user --value="$(grep -Po 'no-user-rc \K.*$' /home/$ssh_user/.ssh/authorized_keys)"
+fi