diff --git a/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.h b/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.h
index 73ea92b5a1..0defa56e81 100644
--- a/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.h
+++ b/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.h
@@ -26,10 +26,6 @@
 #include <Library/DebugLib.h>
 #include <Library/BaseLib.h>
 
-#ifndef ARRAY_SIZE
-#define ARRAY_SIZE(Array) (sizeof(Array) / sizeof(*Array))
-#endif
-
 /**
   Checks if the input string matches to the regular expression pattern.