diff --git a/MdeModulePkg/Universal/RegularExpressionDxe/Oniguruma/regerror.c b/MdeModulePkg/Universal/RegularExpressionDxe/Oniguruma/regerror.c
index 222e8e6136..d92b61e229 100644
--- a/MdeModulePkg/Universal/RegularExpressionDxe/Oniguruma/regerror.c
+++ b/MdeModulePkg/Universal/RegularExpressionDxe/Oniguruma/regerror.c
@@ -28,7 +28,6 @@
  */
 
 #include "regint.h"
-#define HAVE_STDARG_PROTOTYPES
 #if 0
 #include <stdio.h> /* for vsnprintf() */
 
diff --git a/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.inf b/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.inf
index da50092cd2..df54716182 100644
--- a/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.inf
+++ b/MdeModulePkg/Universal/RegularExpressionDxe/RegularExpressionDxe.inf
@@ -79,6 +79,9 @@
   gEfiRegularExpressionProtocolGuid       ## PRODUCES
 
 [BuildOptions]
+  # Enable STDARG for variable arguments
+  *_*_*_CC_FLAGS = -DHAVE_STDARG_H
+
   # Override MSFT build option to remove /Oi and /GL
   MSFT:*_*_*_CC_FLAGS          = /GL-
   INTEL:*_*_*_CC_FLAGS         = /Oi-