diff --git a/util/postinstall.sh.in b/util/postinstall.sh.in
index 8ec4604d..1f8db6c4 100755
--- a/util/postinstall.sh.in
+++ b/util/postinstall.sh.in
@@ -419,7 +419,7 @@ SOCKHELPER
 
 webui_install() {
    chmod 770 "${DOCROOT}/tmp" "${DOCROOT}/images"
-   chown "$PILERUSER" "${DOCROOT}/tmp"
+   chown "${PILERUSER}:${WWWGROUP}" "${DOCROOT}/tmp"
 
    envsubst < "${SCRIPT_DIR}/config-site.php.in" | sed s%config%\$config%g > "$CONFIG_SITE_PHP"