That works. My habit is to make the fix, commit it as "!fixup whatever", start an interactive rebase, move the fixup commit just after the bad commit (M-↑), press f on the fixup commit to tell rebase to merge it with the bad commit, and run the rebase (C-c C-c). This is pretty much the same method as yours, but committing first means the fixup will still be there if you have to cancel & redo the rebase for some reason, such as unexpected and confusing merge conflicts.