diff -burN tcsh-6.20.00.orig/tw.parse.c tcsh-6.20.00/tw.parse.c
--- tcsh-6.20.00.orig/tw.parse.c	2015-10-16 17:59:56.000000000 +0300
+++ tcsh-6.20.00/tw.parse.c	2017-07-20 11:44:02.741303110 +0300
@@ -2173,6 +2173,8 @@
 	     (Strchr(val, 'x') != NULL);
 
     for (i = 0; i < count; i++)	{ /* find widest string */
+	/* check before converting to uint */
+	if (NLSStringWidth(items[i]) > 0)
 	maxwidth = max(maxwidth, (unsigned int) NLSStringWidth(items[i]));
     }