Changing binary files to text.

I have a few text files that I recently realized had been incorrectly
checked in as binary files and not text files, presumably because
their extension (*.sql) wasn't recognized as a text file by the
default filter (I didn't configure any extensions, and stupidly didn't
verify the files were recognized as text when I originally checked
them in). I realized it when I attempted to do a cvs diff on the
files.

Is there some trick I can do to make CVS think they're text instead of
binary without losing the past revisions that are already in the
repository? I'd rather not remove then re-add the files, because I'd
like to preserve past revision tags and change logs. I don't mind if
the solution is really hacky.

Thanks,
Jason