diff --git a/Makefile b/Makefile
index db4d072..a4692a2 100644
--- a/Makefile
+++ b/Makefile
@@ -17,6 +17,6 @@ build: noroot mkoutdir common.mk $(OUTPUTS) force
 	find ! -regex '.*/\..*' -type d ! -group www -print0 | xargs -r0 chgrp www || true
 
 noroot:
-	if test $$UID = 0; then echo "don't build as root!"; exit 1; fi
+	if test $$(id -u) = 0; then echo "don't build as root!"; exit 1; fi
 
 $(OUTDIR)index.html: events.xml news.xml