diff --git a/MdePkg/Library/BasePciCf8Lib/PciLib.c b/MdePkg/Library/BasePciCf8Lib/PciLib.c
index c5880bdeee..0e536ce696 100644
--- a/MdePkg/Library/BasePciCf8Lib/PciLib.c
+++ b/MdePkg/Library/BasePciCf8Lib/PciLib.c
@@ -53,7 +53,9 @@
 
 **/
 #define PCI_TO_CF8_ADDRESS(A) \
-  ((UINT32)(((A) >> 4) | ((A) & 0xfc) | 0x80000000))
+  ((UINT32) ((((A) >> 4) & 0xffffff00) | ((A) & 0xfc) | 0x80000000))
+  
+
 
 /**
   Reads an 8-bit PCI configuration register.