Reverting accidental permanent acceptance of SSL certificate?

I made a mistake when running a svn checkout towards my server!
I was *not* connected by vpn when I issued the request but rather than
having a "no connect" message I saw the certificate dialogue and since
my server uses a self-signed certificate I did not look closely but
set it to accept *permanently*....

How can I revert this? Is there a client svn command to un-accept a
certificate? All I find when googling is the opposite, i.e. how to
accept a certificate...

-- 
Bo Berglund
Developer in Sweden