Run mod_dav_svn with v2 protocol disabled under a debugger. Set a breakpoint on dav_svn__checkout. Run a command such as svn cp -mm http://server/repo/trunk ^/tags/T1 the server will stop at the dav_svn__checkout breakpoint. Now run another non-conflicting commit so that the first commit is based on an old revision (I'm using ra_local because the server is stopped): svn cp -mm file://`pwd`/repo/trunk ^/tags/T2 then allow the server to continue. The first commit fails when using serf: svn: E190003: The specified baseline is not the latest baseline, so it may not be checked out. but completes when using neon. This is because neon detects the SVN_ERR_APMOD_BAD_BASELINE error returned by mod_dav_svn and retries the checkout.