diff --git a/include/mapidefs.h b/include/mapidefs.h
index 2c89c0f9ccb..219177d62ee 100644
--- a/include/mapidefs.h
+++ b/include/mapidefs.h
@@ -27,6 +27,7 @@
 #ifndef _OBJBASE_H_
 #include <objbase.h>
 #endif
+#include <stddef.h>
 
 /* Some types from other headers */
 #ifndef __LHANDLE
diff --git a/include/mapival.h b/include/mapival.h
index 2a653a3cca9..82cd020db9d 100644
--- a/include/mapival.h
+++ b/include/mapival.h
@@ -24,6 +24,8 @@ extern "C" {
 #endif
 
 #include <mapiutil.h>
+#include <stddef.h>
+#include <stdarg.h>
 
 BOOL  WINAPI FBadRglpszW(LPWSTR*,ULONG);
 BOOL  WINAPI FBadRowSet(LPSRowSet);