Folding commits together

I've made a couple of trivial commits I'd like to fold into a single commit now. 
In the manpage of git-rebase I saw a recipe how to do it using rebase -i and it 
seemed quite trivial, but it doesn't work for me. I'm in a clean state on branch 
master and want fold the last 3 commits into one - this is probably the most 
trivial use case. Whatever I try I get an empty .git/rebase-merge/git-rebase-
todo, so I can't get to the point of using <<If you want to fold two or more 
commits into one, replace the command "pick" for the second and subsequent 
commits with "squash" or "fixup".>>