diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index f51d376..c2f5117 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -3675,6 +3675,11 @@ static int pci_probe(struct pci_dev *dev,
 
 	reg_write(ohci, OHCI1394_IsoXmitIntMaskSet, ~0);
 	ohci->it_context_support = reg_read(ohci, OHCI1394_IsoXmitIntMaskSet);
+	/* JMicron JMB38x often shows 0 at first read, just ignore it */
+	if (!ohci->it_context_support) {
+		ohci_notice(ohci, "overriding IsoXmitIntMask\n");
+		ohci->it_context_support = 0xf;
+	}
 	reg_write(ohci, OHCI1394_IsoXmitIntMaskClear, ~0);
 	ohci->it_context_mask = ohci->it_context_support;
 	ohci->n_it = hweight32(ohci->it_context_mask);