diff --git a/qemu/hw/rtl8139.c b/qemu/hw/rtl8139.c
index 94fc2fc..e345888 100644
--- a/qemu/hw/rtl8139.c
+++ b/qemu/hw/rtl8139.c
@@ -408,6 +408,8 @@ typedef struct RTL8139TallyCounters
     uint16_t   TxUndrn;
 } RTL8139TallyCounters;
 
+#define RTL8139_PNPNMIO_SIZE	0x1000
+
 /* Clears all tally counters */
 static void RTL8139TallyCounters_clear(RTL8139TallyCounters* counters);
 
@@ -3325,7 +3327,7 @@ static void rtl8139_mmio_map(PCIDevice *pci_dev, int region_num,
     PCIRTL8139State *d = (PCIRTL8139State *)pci_dev;
     RTL8139State *s = &d->rtl8139;
 
-    cpu_register_physical_memory(addr + 0, 0x100, s->rtl8139_mmio_io_addr);
+    cpu_register_physical_memory(addr + 0, RTL8139_PNPNMIO_SIZE, s->rtl8139_mmio_io_addr);
 }
 
 static void rtl8139_ioport_map(PCIDevice *pci_dev, int region_num, 
@@ -3438,10 +3440,10 @@ void pci_rtl8139_init(PCIBus *bus, NICInfo *nd, int devfn)
     s->rtl8139_mmio_io_addr =
     cpu_register_io_memory(0, rtl8139_mmio_read, rtl8139_mmio_write, s);
 
-    pci_register_io_region(&d->dev, 0, 0x100, 
+    pci_register_io_region(&d->dev, 0, RTL8139_PNPNMIO_SIZE, 
                            PCI_ADDRESS_SPACE_IO,  rtl8139_ioport_map);
 
-    pci_register_io_region(&d->dev, 1, 0x100, 
+    pci_register_io_region(&d->dev, 1, RTL8139_PNPNMIO_SIZE, 
                            PCI_ADDRESS_SPACE_MEM, rtl8139_mmio_map);
 
     s->irq = 16; /* PCI interrupt */