Puzzle 49330

I saw this solution.

1... Rcxc2+
2. Kd1 Rd2+
3. Kc1 Nd3+
4. Kb1 Rab2+
5. Ka1 Rd1#

Obviously my solution is one move longer than 4... Rdb2#.
But I think my solution shouldn't fail the puzzle.

Is this a candidate for "Good move, but you can do better."?

Here's the link to the puzzle:
http://en.lichess.org/training/49330

And here you can see that my line also leads to checkmate:
http://en.lichess.org/l8v2swZrIn3x

If you miss a mate in one you can't comment on this page.

;)
{text is too short, blabla}