diff --git a/rootfs/etc/cont-init.d/udev.sh b/rootfs/etc/cont-init.d/udev.sh
index 7a8c6402b..c79aa3960 100644
--- a/rootfs/etc/cont-init.d/udev.sh
+++ b/rootfs/etc/cont-init.d/udev.sh
@@ -2,7 +2,7 @@
 # ==============================================================================
 # Start udev service if env USING_UDEV is true
 # ==============================================================================
-if ! bashio::var.true "${USING_UDEV}"; then
+if ! bashio::var.true "${USING_UDEV+x}"; then
     bashio::exit.ok
 fi