diff -Naur graphviz-2.6-orig/lib/ast/pathpath.c graphviz-2.6/lib/ast/pathpath.c
--- graphviz-2.6-orig/lib/ast/pathpath.c	2005-10-30 15:15:30.000000000 +0100
+++ graphviz-2.6/lib/ast/pathpath.c	2005-10-30 15:16:20.000000000 +0100
@@ -33,7 +33,12 @@
 #include <unistd.h>
 
 /* #include <option.h> */
+#ifdef __APPLE__
+#include <crt_externs.h>
+#define environ (*_NSGetEnviron())
+#else
 extern char **environ;
+#endif
 char **opt_info_argv;
 
 char *pathpath(register char *path, const char *p, const char *a, int mode)