diff --git a/src/pciinit.c b/src/pciinit.c
index 7d2ea00..f9ebd61 100644
--- a/src/pciinit.c
+++ b/src/pciinit.c
@@ -136,16 +136,23 @@ static void pci_bios_init_device(u16 bdf)
         /* default memory mappings */
         for (i = 0; i < PCI_NUM_REGIONS; i++) {
             int ofs;
-            u32 val, size;
-
+            u32 val, mask, size;
             if (i == PCI_ROM_SLOT)
                 ofs = PCI_ROM_ADDRESS;
             else
                 ofs = PCI_BASE_ADDRESS_0 + i * 4;
-            pci_config_writel(bdf, ofs, 0xffffffff);
+
+            val = pci_config_readl(bdf, ofs);
+            if (i == PCI_ROM_SLOT)
+		mask = PCI_ROM_ADDRESS_MASK;
+            else if (val & PCI_BASE_ADDRESS_SPACE_IO)
+                mask = PCI_BASE_ADDRESS_IO_MASK;
+            else
+                mask = PCI_BASE_ADDRESS_MEM_MASK;
+            pci_config_writel(bdf, ofs, val | mask);
             val = pci_config_readl(bdf, ofs);
             if (val != 0) {
-                size = (~(val & ~0xf)) + 1;
+                size = (~(val & mask)) + 1;
                 if (val & PCI_BASE_ADDRESS_SPACE_IO)
                     paddr = &pci_bios_io_addr;
                 else if (size >= 0x04000000)