--- a/thermferm/devices.c	Sat Apr 20 11:48:20 2024 +0200
+++ b/thermferm/devices.c	Mon Apr 22 11:33:04 2024 +0200
@@ -355,7 +355,7 @@
     int			tmp, present;
 
     if (uuid == NULL)
-	return 0;
+	return DEVPRESENT_UNDEF;
 
     for (device = Config.devices; device; device = device->next) {
 	if (! strcmp(uuid, device->uuid)) {