Tie entry behaves incorrectly in measure with existing notes

Ubuntu Studio 14.04, GIT commit: e7146ba

1) new score
2) first measure, enter note input mode
3) C D E F
4) move cursor back to the D on beat two (still in note input mode)
5) type "D" again to re-enter it
6) press "+"

Result: a second unison "D" is added to the chord
Expected result: a "D" is entered onto the third beat (replacing the "E") and they are tied

BTW, the need for step 5 in order to retroactively enter ties in note entry mode has always seemed like a bug to me, although I've come to accept it.