parallel: Input is tty

[Rob Syme]

I am trying to execute a script on a directory of files on a remote
computer via ssh:

[rob@local]$ tty
/dev/pts/61
[rob@local]$ ssh rob@remote.com
[rob@remote]$ tty
/dev/pts/2
[rob@remote]$ parallel -j 6 example_script.py -- *.fasta
parallel: Input is tty. Press CTRL-D to exit.

The same command works very well on my local machine from the same
files. My understanding is that both the local and remote terminals
are tty, so I'm confused as to why one raises an error and the other
is fine. Any pointers are appreciated.
-r

Rob Syme