diff -u -r ../mdocml-1.14.1/term_ascii.c ./term_ascii.c
--- ../mdocml-1.14.1/term_ascii.c	2017-02-21 00:25:20.000000000 +0000
+++ ./term_ascii.c	2017-03-02 14:04:37.164590198 +0000
@@ -18,8 +18,10 @@
 #include "config.h"
 
 #include <sys/types.h>
+#include <sys/ioctl.h>
 
 #include <assert.h>
+#include <fcntl.h>
 #if HAVE_WCHAR
 #include <locale.h>
 #endif
@@ -64,12 +66,22 @@
 	char		*v;
 #endif
 	struct termp	*p;
+	struct winsize	ws;
+	int		tfd;
 
 	p = mandoc_calloc(1, sizeof(struct termp));
 
 	p->line = 1;
 	p->tabwidth = 5;
 	p->defrmargin = p->lastrmargin = 78;
+	if ((tfd = open("/dev/tty", O_RDWR, 0)) != -1) {
+		if (ioctl(tfd, TIOCGWINSZ, &ws) != -1) {
+			if (ws.ws_col < 80)
+				p->defrmargin = p->lastrmargin = ws.ws_col - 2;
+		}
+		close(tfd);
+	}
+
 	p->fontq = mandoc_reallocarray(NULL,
 	     (p->fontsz = 8), sizeof(enum termfont));
 	p->fontq[0] = p->fontl = TERMFONT_NONE;