Index: sys/amd64/acpica/acpi_machdep.c
===================================================================
--- sys/amd64/acpica/acpi_machdep.c
+++ sys/amd64/acpica/acpi_machdep.c
@@ -359,7 +359,7 @@
 		panic("failed to add acpi0 device");
 
 	error = bus_generic_attach(dev);
-	if (error == 0)
+	if (error == 0 && device_get_softc(acpi_dev) != NULL)
 		acpi_install_wakeup_handler(device_get_softc(acpi_dev));
 
 	return (error);