diff --git a/scripts/remove b/scripts/remove
index 4ae87b4..e0dc339 100755
--- a/scripts/remove
+++ b/scripts/remove
@@ -1,5 +1,8 @@
 #!/bin/bash
 
+# Treat unset variables as an error
+set -u
+
 # This is a multi-instance app, meaning it can be installed several times independently
 # The id of the app as stated in the manifest is available as $YNH_APP_ID
 # The instance number is available as $YNH_APP_INSTANCE_NUMBER (equals "1", "2", ...)
diff --git a/scripts/upgrade b/scripts/upgrade
index 9056584..3d2eedb 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -1,7 +1,7 @@
 #!/bin/bash
 
-# causes the shell to exit if any subcommand or pipeline returns a non-zero status
-set -e
+# Exit on command errors and treat unset variables as an error
+set -eu
 
 # This is a multi-instance app, meaning it can be installed several times independently
 # The id of the app as stated in the manifest is available as $YNH_APP_ID
@@ -15,12 +15,12 @@ set -e
 # db names, ...
 app=$YNH_APP_INSTANCE_NAME
 
-# Retrieve arguments
-domain=$YNH_APP_ARG_DOMAIN
-path=$YNH_APP_ARG_PATH
-admin_user=$YNH_APP_ARG_ADMIN_USER
-upload_password=$YNH_APP_ARG_UPLOAD_PASSWORD
-is_public=$YNH_APP_ARG_IS_PUBLIC
+# Retrieve settings
+domain=$(sudo yunohost app setting $app domain)
+path=$(sudo yunohost app setting $app path)
+admin_user=$(sudo yunohost app setting $app admin_user)
+upload_password=$(sudo yunohost app setting $app upload_password)
+is_public=$(sudo yunohost app setting $app is_public)
 
 # Remove trailing "/" for next commands
 path=${path%/}