diff --git a/sys/dev/agp/agp_via.c b/sys/dev/agp/agp_via.c
--- a/sys/dev/agp/agp_via.c
+++ b/sys/dev/agp/agp_via.c
@@ -179,6 +179,7 @@
 	sc->initial_aperture = AGP_GET_APERTURE(dev);
 	if (sc->initial_aperture == 0) {
 		device_printf(dev, "bad initial aperture size, disabling\n");
+		agp_generic_detach(dev);
 		return ENXIO;
 	}