diff --git a/arch/i386/pci/fixup.c b/arch/i386/pci/fixup.c
index be52c5a..8e8e895 100644
--- a/arch/i386/pci/fixup.c
+++ b/arch/i386/pci/fixup.c
@@ -253,7 +253,7 @@
 #define MAX_PCIEROOT	6
 static int quirk_aspm_offset[MAX_PCIEROOT << 3];
 
-#define GET_INDEX(a, b) (((a - PCI_DEVICE_ID_INTEL_MCH_PA) << 3) + b)
+#define GET_INDEX(a, b) ((((a) - PCI_DEVICE_ID_INTEL_MCH_PA) << 3) + ((b) & 7))
 
 static int quirk_pcie_aspm_read(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 *value)
 {