diff --git a/src/devices/device_util.c b/src/devices/device_util.c
index 9081a36ea2..84fb11505c 100644
--- a/src/devices/device_util.c
+++ b/src/devices/device_util.c
@@ -583,6 +583,8 @@ void search_bus_resources(struct bus *bus, unsigned long type_mask,
 					if (subbus->link_num
 					== IOINDEX_SUBTRACTIVE_LINK(res->index))
 						break;
+				if (!subbus) /* Why can subbus be NULL?  */
+					break;
 				search_bus_resources(subbus, type_mask, type,
 						     search, gp);
 				continue;