Okay, I followed Nick Holland's suggestion.
First, I had setup an OpenBSD 3.9 test machine. The only configuration
I did was to setup the ftpd service as described in a previous post. I
tested it, the problem still persisted. Then I download src.tar.gz from
the 3.8 directory on a mirror and extracted it into /usr/src. Then in
/usr/src/libexec/ftpd, I did make obj, make cleandir, make depend, make,
make install. Finally I rebooted. I did a test and it was successful.
So it appears something did change. Does this mean I should read up
sendbug and figure out how to report a bug or was this change intentional?