Planning Poker and wordy developers [closed]

Question

My team is composed of 4 developers; all seasoned and skilled. One of them is a wordy, well intended chap who insists on defining the technical solution to our stories before we put down our estimates with Planning Poker. He refuses to estimate if he doesn't have a rough idea of the agreed technical solution (which sounds reasonable, right?).

The problem is that our estimating sessions are taking forever to finish!! In your experience, how do you deal with this kind of personality when playing the planning poker?