Index: head/sys/dev/acpica/acpi_pci_link.c
===================================================================
--- head/sys/dev/acpica/acpi_pci_link.c
+++ head/sys/dev/acpica/acpi_pci_link.c
@@ -580,6 +580,9 @@
 	uint8_t func, maxfunc;
 
 	/* See if we have a valid device at function 0. */
+	value = pci_cfgregread(bus, device, 0, PCIR_VENDOR, 2);
+	if (value == PCIV_INVALID)
+		return (PCI_INVALID_IRQ);
 	value = pci_cfgregread(bus, device, 0, PCIR_HDRTYPE, 1);
 	if ((value & PCIM_HDRTYPE) > PCI_MAXHDRTYPE)
 		return (PCI_INVALID_IRQ);
@@ -590,8 +593,8 @@
 
 	/* Scan all possible functions at this device. */
 	for (func = 0; func <= maxfunc; func++) {
-		value = pci_cfgregread(bus, device, func, PCIR_DEVVENDOR, 4);
-		if (value == 0xffffffff)
+		value = pci_cfgregread(bus, device, func, PCIR_VENDOR, 2);
+		if (value == PCIV_INVALID)
 			continue;
 		value = pci_cfgregread(bus, device, func, PCIR_INTPIN, 1);
 
Index: head/sys/i386/pci/pci_pir.c
===================================================================
--- head/sys/i386/pci/pci_pir.c
+++ head/sys/i386/pci/pci_pir.c
@@ -257,8 +257,8 @@
 }
 
 /*
- * Look to see if any of the function on the PCI device at bus/device have
- * an interrupt routed to intpin 'pin' by the BIOS.
+ * Look to see if any of the functions on the PCI device at bus/device
+ * have an interrupt routed to intpin 'pin' by the BIOS.
  */
 static uint8_t
 pci_pir_search_irq(int bus, int device, int pin)
@@ -267,6 +267,9 @@
 	uint8_t func, maxfunc;
 
 	/* See if we have a valid device at function 0. */
+	value = pci_cfgregread(bus, device, 0, PCIR_VENDOR, 2);
+	if (value == PCIV_INVALID)
+		return (PCI_INVALID_IRQ);
 	value = pci_cfgregread(bus, device, 0, PCIR_HDRTYPE, 1);
 	if ((value & PCIM_HDRTYPE) > PCI_MAXHDRTYPE)
 		return (PCI_INVALID_IRQ);
@@ -277,8 +280,8 @@
 
 	/* Scan all possible functions at this device. */
 	for (func = 0; func <= maxfunc; func++) {
-		value = pci_cfgregread(bus, device, func, PCIR_DEVVENDOR, 4);
-		if (value == 0xffffffff)
+		value = pci_cfgregread(bus, device, func, PCIR_VENDOR, 2);
+		if (value == PCIV_INVALID)
 			continue;
 		value = pci_cfgregread(bus, device, func, PCIR_INTPIN, 1);