diff --git a/scripts/install b/scripts/install
index 1bbfee9..c284506 100644
--- a/scripts/install
+++ b/scripts/install
@@ -94,7 +94,7 @@ ynh_app_setting_set "$app" language "$language"
 ###		- And the section "UPGRADE DEPENDENCIES" in the upgrade script
 
 pid=$(pgrep -f '/usr/bin/python3 /usr/bin/unattended-upgrade --download-only')
-if [ ! -z $pid ] ;then
+if [ ! -z "$pid" ] ;then
     ynh_script_progression --message="Check and wait end of unattended-upgrade of package_check" -w 1
     tail --pid=$pid -f /dev/null
 fi