diff --git a/PcAtChipsetPkg/Include/Library/IoApicLib.h b/PcAtChipsetPkg/Include/Library/IoApicLib.h
index bd9054be53..c3eb0ce4b3 100644
--- a/PcAtChipsetPkg/Include/Library/IoApicLib.h
+++ b/PcAtChipsetPkg/Include/Library/IoApicLib.h
@@ -14,6 +14,8 @@
   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
 **/
+#ifndef __IO_APIC_LIB_H__
+#define __IO_APIC_LIB_H__
 
 /**
   Read a 32-bit I/O APIC register.
@@ -100,3 +102,4 @@ IoApicConfigureInterrupt (
   IN BOOLEAN  LevelTriggered,
   IN BOOLEAN  AssertionLevel
   );
+#endif