diff -up graphviz-2.30.1/cmd/tools/gv2gml.c.orig5 graphviz-2.30.1/cmd/tools/gv2gml.c

--- graphviz-2.30.1/cmd/tools/gv2gml.c.orig5	2013-02-14 14:27:39.000000000 +0100

+++ graphviz-2.30.1/cmd/tools/gv2gml.c	2013-07-11 13:54:56.661096922 +0200

@@ -712,7 +712,7 @@ static void initargs(int argc, char **ar

     CmdName = cmdName(argv[0]);

     opterr = 0;

-    while ((c = getopt(argc, argv, ":io:")) != -1) {

+    while ((c = getopt(argc, argv, "o:")) != -1) {

 	switch (c) {

 	case 'o':

 	    outFile = openFile(optarg, "w");