tramp (2.2.5-pre); Unknown file I/O primitive

Enter your bug report in this message, including as much detail
as you possibly can about the problem, what you did to cause it
and what the local and remote machines are.

If you can give a simple set of instructions to make this bug
happen reliably, please include those.  Thank you for helping
kill bugs in Tramp.

Before reproducing the bug, you might apply

  M-x tramp-cleanup-all-connections

This allows to investigate from a clean environment.  Another
useful thing to do is to put

  (setq tramp-verbose 9)

in the ~/.emacs file and to repeat the bug.  Then, include the
contents of the *tramp/foo* buffer and the *debug tramp/foo*
buffer in your bug report.

--bug report follows this line--


--8<---------------cut here---------------start------------->8---
Debugger entered--Lisp error: (error "unknown file I/O primitive: file-in-directory-p")
  signal(error ("unknown file I/O primitive: file-in-directory-p"))
  error("unknown file I/O primitive: %s" file-in-directory-p)
  tramp-file-name-for-operation(file-in-directory-p "/sudo:root <at> localhost:/opt/local/etc/postfix/" "/sudo:root <at> localhost:/etc/postfix/certs")