--- researchv9/cmd/troff/t6.c	2018/04/24 17:21:59	1.1.1.1
+++ researchv9/cmd/troff/t6.c	2018/04/24 17:23:34	1.1.1.2
@@ -641,7 +641,7 @@ char *truename;
 		shortname[1] = f >> BYTE;
 		shortname[2] = '\0';
 	}
-	if (truename[0] == '/')	/* full pathname -- use verbatim.out */
+	if (truename && truename[0] == '/')	/* full pathname -- use verbatim.out */
 		sprintf(longname, "%s.out", truename);
 	else
 		sprintf(longname, "%s/dev%s/%s.out", fontdir, devname, shortname);