rebase problem

A co-worker this on our local u-boot repo:
  git checkout master
  git fetch denx/master
  git merge denx/master
<resolve conflicts>
  git commit
  ...
  git commit
Now u-boot is working again
then update to latest u-boot so:
  git fetch denx/master
  git rebase denx/master
Now it is a mess, that rebase seems to start from way back as a
staring reference, not from the last merge shown above.
I guess I forgotten how git works, what did go wrong?

  Jocke