git-fast-import question

I've been writing an importer from an older SCM into git.  I'm getting
the following behavior with using git-fast-import:

The file I'm importing has something along the lines of:

commit refs/heads/foo
<various metadata>
M 100644 :mark path/to/some/file

Then, later on, there's another commit:

commit refs/heads/foo
<various metadata>
R path/to/some/file new/path/to/some/file

As far as I've been able to see, the :from tag points to the correct
commit (which is also in the correct branch).  There are no instances
of 'reset <branch>' being called anywhere.  The file isn't deleted
anywhere.

But when I run fast-import, I receive an error to the extent of:
fatal:  Path path/to/some/file not in branch

So to me, it looks like the file that I'm renaming should exist in the
branch - it's not being renamed anywhere, not being deleted, and the
branch isn't reset.  Yet fast-import doesn't seem to think the file
exists.

I'm using git 1.6.3.3