[O] Tbl: addition of two times results in error

[Karl Voit]

,----[ http://orgmode.org/org.html#Durations-and-time-values ]
|      | Task 1 | Task 2 |   Total |
|      |--------+--------+---------|
|      |  35:00 |  35:00 | 1:10:00 |
|      #+TBLFM: @2$3=$1+$2;T
`----

... results in #ERROR at @2$3 on my system with current Org-mode (I
did «git pull» right now):

,----[ debug message ]
| Substitution history of formula
| Orig:   $1+$2;T
| $xyz->  $1+$2
| @r$c->  $1+$2
| $1->    (35:00)+(35:00)
|        ------^
| Error:  Bad format
`----

Where is the problem?

-- 
Karl Voit