diff --git a/Dockerfile b/Dockerfile
index f96224d..8cabb07 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -18,7 +18,7 @@ RUN <<EOF
 		php8.3-xml socat
 	a2dismod mpm_event
 	a2enmod mpm_prefork
-	adduser --system --in-group www-data \
+	adduser --system --ingroup www-data \
 		--shell '/usr/bin/php /opt/lwb5/scripts/ticks.php' \
 		--comment 'LWB5 Ticks' \
 		--home /opt/lwb5 --no-create-home \