diff --git a/compat.h b/compat.h
new file mode 100644
index 000000000..e7fe144c1
--- /dev/null
+++ b/compat.h
@@ -0,0 +1,69 @@
+/*
+ *  CU sudo version 1.3.1
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 1, or (at your option)
+ *  any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ *  Please send bugs, changes, problems to sudo-bugs@cs.colorado.edu
+ */
+
+#ifndef _SUDO_COMPAT_H
+#define _SUDO_COMPAT_H
+
+/*
+ * Macros that may be missing on some Operating Systems
+ */
+
+/* Deal with ansi stuff reasonably.  */
+#ifndef  __P
+#  if defined (__cplusplus) || defined (__STDC__)
+#    define __P(args)     args
+#  else
+#    define __P(args)     ()
+#  endif
+#endif /* __P */
+
+/*
+ * Some systems (ie ISC V/386) do not define MAXPATHLEN even in param.h
+ */
+#ifndef MAXPATHLEN
+#  define MAXPATHLEN		1024
+#endif
+
+/*
+ * Some systems do not define MAXHOSTNAMELEN.
+ */
+#ifndef MAXHOSTNAMELEN
+#  define MAXHOSTNAMELEN	64
+#endif
+
+/*
+ * Emulate seteuid() and setegid() for HP-UX
+ */
+#ifdef __hpux
+#  define seteuid(__EUID)	(setresuid((uid_t)-1, __EUID, (uid_t)-1))
+#  define setegid(__EGID)	(setresgid((gid_t)-1, __EGID, (gid_t)-1))
+#endif	/* __hpux */
+#endif	/* __hpux */
+
+/*
+ * Emulate seteuid() and setegid() for AIX
+ */
+#ifdef _AIX
+#  include <sys/id.h>
+#  define seteuid(__EUID)	(setuidx(ID_EFFECTIVE|ID_REAL, __EUID))
+#  define setegid(__EGID)	(setgidx(ID_EFFECTIVE|ID_REAL, __EGID))
+#endif	/* _AIX */
+
+#endif /* _SUDO_COMPAT_H */