--- ray/src/px/ra_pr24.c	1992/10/30 09:08:33	2.6
+++ ray/src/px/ra_pr24.c	1993/11/18 09:55:14	2.7
@@ -80,7 +80,7 @@ char  *argv[];
 		exit(1);
 	}
 	if (i == argc-2 && freopen(argv[i+1], "w", stdout) == NULL) {
-		fprintf(stderr, "can't open output \"%s\"\n",
+		fprintf(stderr, "%s: can't open output \"%s\"\n",
 				progname, argv[i+1]);
 		exit(1);
 	}