diff --git a/usr.bin/localedef/wide.c b/usr.bin/localedef/wide.c
index 791f52ab1f7..f1e05c5f16f 100644
--- a/usr.bin/localedef/wide.c
+++ b/usr.bin/localedef/wide.c
@@ -37,6 +37,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <ctype.h>
 #include <stdlib.h>
 #include <wchar.h>
 #include <string.h>