diff --git a/scripts/_common.sh b/scripts/_common.sh
index 8bb05b4..b062844 100644
--- a/scripts/_common.sh
+++ b/scripts/_common.sh
@@ -18,3 +18,38 @@ pkg_dependencies="deb1 deb2"
 #=================================================
 # FUTURE OFFICIAL HELPERS
 #=================================================
+
+# Check if a permission exists
+#
+# While waiting for this new helper https://github.com/YunoHost/yunohost/pull/905
+# We have to use another one because the new helper use a new YunoHost command, not available for now.
+#
+# usage: ynh_permission_has_user --permission=permission --user=user
+# | arg: -p, --permission - the permission to check
+# | arg: -u, --user - the user seek in the permission
+#
+# example: ynh_permission_has_user --permission=main --user=visitors
+#
+# Requires YunoHost version 3.7.1 or higher.
+ynh_permission_has_user() {
+    local legacy_args=pu
+    # Declare an array to define the options of this helper.
+    declare -Ar args_array=( [p]=permission= [u]=user= )
+    local permission
+    local user
+    # Manage arguments with getopts
+    ynh_handle_getopts_args "$@"
+
+    if ! ynh_permission_exists --permission=$permission
+    then
+        return 1
+    fi
+
+    # List all permissions
+    # Filter only the required permission with a multiline sed (Here a cut from the permission to the next one), remove the url and his value 
+    perm="$(yunohost user permission list --full --output-as plain | sed --quiet "/^#$app.$permission/,/^#[[:alnum:]]/p" | sed "/^##url/,+1d")"
+    # Remove all lines starting by # (got from the plain output before)
+    allowed_users="$(echo "$perm" | grep --invert-match '^#')"
+    # Grep the list of users an return the result if the user is indeed into the list
+    echo "$allowed_users" | grep --quiet --word "$user"
+}
diff --git a/scripts/upgrade b/scripts/upgrade
index 97815e3..544b891 100755
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -59,17 +59,19 @@ fi
 is_public=$(ynh_app_setting_get --app=$app --key=is_public)
 
 if [ -n "$is_public" ]; then
-	# Remove skipped_uris
-	ynh_app_setting_delete --app=$app --key=skipped_uris
 	# Remove unprotected_uris
 	ynh_app_setting_delete --app=$app --key=unprotected_uris
 	# Remove protected_uris
 	ynh_app_setting_delete --app=$app --key=protected_uris
 
 	# Removing skipped/unprotected_uris under certain conditions, remove the visitors group added during the migration process of 3.7
-	# If the app was public, add visitors again to the main permission
-	if [ $is_public -eq 1 ]; then
+	# Remove skipped_uris. If the app was public, add visitors again to the main permission
+	if ynh_permission_has_user --permission=main --user=visitors
+	then
+		ynh_app_setting_delete --app=$app --key=skipped_uris
 		ynh_permission_update --permission "main" --add "visitors"
+	else
+		ynh_app_setting_delete --app=$app --key=skipped_uris
 	fi
 	ynh_app_setting_delete --app=$app --key=is_public
 fi