Builds not triggered for new branches

Hi - I have a build configuration that is set up with a VCS trigger to match certain branches, but it never seems to trigger the build when branches meeting the criteria are first created, if if the first appearance of the branch includes commits never seen before in other branches.  It only triggers the second time the branch is pushed to.

To be more precise - I have a VCS root whose default branch is `refs/heads/main` and that is set up with this branch specification (so it can  merge requests from gitlab):

+:refs/heads/(main)
+:refs/(merge-requests/*)/head

The build configuration has trigger with this branch filter:

+:merge-requests/*
-:<default>

I then make a new merge request, which `refs/merge-requests/35/head`, which has a brand new commit, never seen on any other branches.  This does not trigger the build.

I then make another push to the merge request, with a 2nd never-before seen commit, and THAT triggers the build.