diff --git a/sys/bus/u4b/controller/uhci_pci.c b/sys/bus/u4b/controller/uhci_pci.c
--- a/sys/bus/u4b/controller/uhci_pci.c
+++ b/sys/bus/u4b/controller/uhci_pci.c
@@ -377,7 +377,7 @@
 	 * disable interrupts that might have been switched on in
 	 * uhci_init.
 	 */
-	if (sc->sc_io_res) {
+	if (sc->sc_io_res && sc->sc_bus.bdev != NULL) {
 		USB_BUS_LOCK(&sc->sc_bus);
 
 		/* stop the controller */