diff --git a/sys/dev/pci/vga_pci.c b/sys/dev/pci/vga_pci.c
index d7ff20f..ab8823a 100644
--- a/sys/dev/pci/vga_pci.c
+++ b/sys/dev/pci/vga_pci.c
@@ -156,12 +156,49 @@ vga_pci_unmap_bios(device_t dev, void *bios)
 	    vr->vr_res);
 }
 
+static void
+vga_pci_check_if_boot_display(device_t dev)
+{
+	device_t pcib;
+	uint16_t config;
+
+	if (vga_pci_default_unit >= 0)
+		return;
+
+	/*
+	 * The primary video card used as a boot display must have the
+	 * "I/O" and "Memory Address Space Decoding" bits set in its
+	 * Command register.
+	 *
+	 * Furthermore, if the card is attached to a bridge, instead of
+	 * the root PCI bus, the bridge must have the "VGA Enable" bit
+	 * set in its Control register.
+	 */
+
+	pcib = device_get_parent(device_get_parent(dev));
+	if (device_get_devclass(device_get_parent(pcib)) ==
+	    devclass_find("pci")) {
+		/*
+		 * The parent bridge is a PCI-to-PCI bridge: check the
+		 * value of the "VGA Enable" bit.
+		 */
+		config = pci_read_config(pcib, PCIR_BRIDGECTL_1, 2);
+		if ((config & PCIB_BCR_VGA_ENABLE) == 0)
+			return;
+	}
+
+	config = pci_read_config(dev, PCIR_COMMAND, 2);
+	if ((config & (PCIM_CMD_PORTEN | PCIM_CMD_MEMEN)) == 0)
+		return;
+
+	vga_pci_default_unit = device_get_unit(dev);
+	device_printf(dev, "Boot video device\n");
+}
+
 static int
 vga_pci_probe(device_t dev)
 {
-	device_t bdev;
 	int unit;
-	uint16_t bctl;
 
 	switch (pci_get_class(dev)) {
 	case PCIC_DISPLAY:
@@ -175,11 +212,9 @@ vga_pci_probe(device_t dev)
 	}
 
 	/* Probe default display. */
+	vga_pci_check_if_boot_display(dev);
+
 	unit = device_get_unit(dev);
-	bdev = device_get_parent(device_get_parent(dev));
-	bctl = pci_read_config(bdev, PCIR_BRIDGECTL_1, 2);
-	if (vga_pci_default_unit < 0 && (bctl & PCIB_BCR_VGA_ENABLE) != 0)
-		vga_pci_default_unit = unit;
 	if (vga_pci_default_unit == unit)
 		device_set_flags(dev, 1);