Unable to turn off strict host checking when rsync'ing between two servers using agent forwarding

I got this command:

ssh -A [email protected] rsync -avz /etc/apache2/ssl [email protected]:/etc/apache2

It throws an error:

Host key verification failed
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: error in rsync protocol data stream (code 12) at io.c(226) [sender=3.1.1]

So I modified the command to this:

ssh -A -o "StrictHostKeyChecking=no" [email protected] rsync -avz -e "ssh -o StrictHostKeyChecking=no" /etc/apache2/ssl [email protected]:/etc/apache2

I still get the same error, however.

UPDATE If I first manually ssh into the example.org machine using agent forwarding and then ssh into 172.30.0.139 from example.org and then exit and then run the rsync command, everything works. I would of course like to avoid having to jump through this extra hoop.