diff --git a/Modules/_localemodule.c b/Modules/_localemodule.c
index 69621e3..1b4aa9d 100644
--- a/Modules/_localemodule.c
+++ b/Modules/_localemodule.c
@@ -13,6 +13,7 @@
 #include <locale.h>
 #include <string.h>
 #include <limits.h>
+#include <ctype.h>
 #include "Python.h"
 #ifdef macintosh
 char *strdup Py_PROTO((char *));