diff --git a/src/sis.h b/src/sis.h
index 2d691a5..70a961b 100644
--- a/src/sis.h
+++ b/src/sis.h
@@ -333,17 +333,18 @@
 #define PCI_CHIP_SIS660			0x6330
 #define PCI_CHIP_SIS340			0x0340
 
-#ifndef PCI_VENDOR_XGI
-#define PCI_VENDOR_XGI		0x18ca
-#endif
 
-#ifndef PCI_CHIP_XGIXG20
+/*
+ * XGI Technology PCI Vendor ID
+ */
+#define PCI_VENDOR_XGI		0x18CA
+
+/*
+ * XGI Technology PCI Device ID
+ */
 #define PCI_CHIP_XGIXG20	0x0020
-#endif
-
-#ifndef PCI_CHIP_XGIXG40
 #define PCI_CHIP_XGIXG40	0x0040
-#endif
+
 
 /* pSiS->Flags (old series only) */
 #define SYNCDRAM		0x00000001