--- arg/arg.orig	2013-10-02 13:57:01 UTC
+++ arg/arg
@@ -5,6 +5,9 @@
         Singleton Class built around getopt() and getopt_long() (3)
 */
 
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <cerrno>
+#endif
 
 #include <string>
 #include <vector>