What they said, just bid 2D. partner will probably bid spades now. If 2S you bid 2N to give him room to bid another suit, which he probably has or rebid spades, after which you set trumps and cuebid. He prolly has some ****** hand with heart void or something, so it is important to hear his shape, support the correct suit and find out keycards. If he has a hand like AQT8xxx, -, Q, AKQ98 you don't want to end up in grand.
It may be hard to suppress your enthusiasm when you have a 16 count opposite a GF hand, but you really must.