diff --git a/kernel/pci/pci.h b/kernel/pci/pci.h
index 89c241b..d38f2e8 100644
--- a/kernel/pci/pci.h
+++ b/kernel/pci/pci.h
@@ -48,6 +48,8 @@ typedef union {
 #define PCI_DEV_PER_BUS   32
 #define PCI_FN_PER_DEV    32
 
+#define PCI_BAR_IOBASE(bar) ((bar) & 0xFFFFFFFC)
+
 uint32_t pci_read32(PciDev dev, uint32_t field);
 uint16_t pci_read16(PciDev dev, uint32_t field);
 uint8_t pci_read8(PciDev dev, uint32_t field);
diff --git a/kernel/pci/qemu_pci_serial/qemu_pci_serial.c b/kernel/pci/qemu_pci_serial/qemu_pci_serial.c
index ec21338..91bcaf8 100644
--- a/kernel/pci/qemu_pci_serial/qemu_pci_serial.c
+++ b/kernel/pci/qemu_pci_serial/qemu_pci_serial.c
@@ -162,7 +162,7 @@ void pci_qemu_pci_serial_init(void) {
 
   LOG("pci", "QEMU_PCI_SERIAL bar0=0x%x\n", bar0);
   
-  uint16_t iobase = bar0 & 0xFFFFFFFC;
+  uint16_t iobase = PCI_BAR_IOBASE(bar0);
   LOG("pci", "QEMU_PCI_SERIAL iobase=0x%x\n", iobase);
 
   QEMU_PCI_SERIAL_DEV.iobase = iobase;