diff --git a/dlls/ntdll/rtlstr.c b/dlls/ntdll/rtlstr.c
index 2ddc404b8ee..0b4e1652950 100644
--- a/dlls/ntdll/rtlstr.c
+++ b/dlls/ntdll/rtlstr.c
@@ -4,10 +4,14 @@
  *	Copyright 1996-1998 Marcus Meissner
  */
 
+#include "config.h"
+
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
-#include <wctype.h>
+#ifdef HAVE_WCTYPE_H
+# include <wctype.h>
+#endif
 #include "wine/winestring.h"
 #include "heap.h"
 #include "winnls.h"