diff --git a/MdePkg/Include/Ipf/ProcessorBind.h b/MdePkg/Include/Ipf/ProcessorBind.h
index eb31c3f7bd..deaf5a292a 100644
--- a/MdePkg/Include/Ipf/ProcessorBind.h
+++ b/MdePkg/Include/Ipf/ProcessorBind.h
@@ -101,7 +101,7 @@
 #endif
 
 
-#if defined(__STDC_VERSION__) && (__STDC_VERSION__ < 199901L)
+#if !defined (__STDC_VERSION__) || (__STDC_VERSION__) < 199901L
   //
   // No ANSI C 2000 stdint.h integer width declarations, so define equivalents
   //