Merge Requests not showing correct diff against master

Hello, I am having troubles with merge requests in GitLab (SaaS)

Steps to reproduce:

  1. Create 2 branches from master
  2. Make a change in branch 1
  3. Make a change in branch 2
  4. Merge changes from branch 1 into master
  5. Do not rebase/merge master into branch 2

Expected: When viewing the changes of a merge request in the diff tab, I’d expect a diff against the master branch like this:

Actual: I see a diff against all the changes that were made in this branch, but not against master

Merge Request:

Master Code:

I can fix this by merging the changes from master into branch 2. My understanding though, would be that the diff view in the merge request shows me the actual difference against master.

Am I/we using merge requests wrong, or is the a config option to change this?

Thanks for your help!

Not sure if this link will help, it seems to be the same problem