diff --git a/scripts/restore b/scripts/restore
index 0289e6e..6826928 100644
--- a/scripts/restore
+++ b/scripts/restore
@@ -11,7 +11,7 @@ ynh_script_progression "Restoring the app main directory..."
 
 ynh_restore "$install_dir"
 
-chown -R $app:www-data "$install_dir"
+chown -R "$app":www-data "$install_dir"
 
 #=================================================
 # RESTORE SYSTEM CONFIGURATIONS
diff --git a/scripts/upgrade b/scripts/upgrade
index 0bfc406..2de10ee 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -61,7 +61,7 @@ ynh_script_progression "Upgrading source files..."
 ynh_setup_source --dest_dir="$install_dir" --full_replace --keep="config.json"
 
 chmod -R o-rwx "$install_dir"
-chown -R $app:www-data "$install_dir"
+chown -R "$app":www-data "$install_dir"
 
 #=================================================
 # ADD A CONFIGURATION