diff -u -r ../tcsh-TCSH6_21_00/sh.h ./sh.h
--- ../tcsh-TCSH6_21_00/sh.h	2019-05-08 18:39:28.000000000 +0000
+++ ./sh.h	2019-05-11 21:11:35.458175126 +0000
@@ -91,6 +91,8 @@
 
 #define TMP_TEMPLATE ".XXXXXX"
 
+#include <wctype.h>
+
 #ifdef SHORT_STRINGS
 # ifdef WIDE_STRINGS
 #include <wchar.h>