diff --git a/target/linux/generic/files/drivers/ssb/fallback-sprom.c b/target/linux/generic/files/drivers/ssb/fallback-sprom.c
index 65436a42ec5..26f0fd2f036 100644
--- a/target/linux/generic/files/drivers/ssb/fallback-sprom.c
+++ b/target/linux/generic/files/drivers/ssb/fallback-sprom.c
@@ -56,9 +56,14 @@ static struct list_head ssb_fbs_list = LIST_HEAD_INIT(ssb_fbs_list);
 
 int ssb_get_fallback_sprom(struct ssb_bus *bus, struct ssb_sprom *out)
 {
-	const u32 pci_bus = bus->host_pci->bus->number;
-	const u32 pci_dev = PCI_SLOT(bus->host_pci->devfn);
 	struct ssb_fbs *pos;
+	u32 pci_bus, pci_dev;
+
+	if (bus->bustype != SSB_BUSTYPE_PCI)
+		return -ENOENT;
+
+	pci_bus = bus->host_pci->bus->number;
+	pci_dev = PCI_SLOT(bus->host_pci->devfn);
 
 	list_for_each_entry(pos, &ssb_fbs_list, list) {
 		if (pos->pci_bus != pci_bus ||