diff --git a/xen/arch/x86/include/asm/pci.h b/xen/arch/x86/include/asm/pci.h
index 6bfe87e278..fd5480d67d 100644
--- a/xen/arch/x86/include/asm/pci.h
+++ b/xen/arch/x86/include/asm/pci.h
@@ -8,10 +8,10 @@
 #define CF8_ADDR_HI(cf8) (  ((cf8) & 0x0f000000U) >> 16)
 #define CF8_ENABLED(cf8) (!!((cf8) & 0x80000000U))
 
-#define IS_SNB_GFX(id) (id == 0x01068086 || id == 0x01168086 \
-                        || id == 0x01268086 || id == 0x01028086 \
-                        || id == 0x01128086 || id == 0x01228086 \
-                        || id == 0x010A8086 )
+#define IS_SNB_GFX(id) ((id) == 0x01068086 || (id) == 0x01168086 \
+                        || (id) == 0x01268086 || (id) == 0x01028086 \
+                        || (id) == 0x01128086 || (id) == 0x01228086 \
+                        || (id) == 0x010A8086 )
 
 struct arch_pci_dev {
     vmask_t used_vectors;