Auto extended warranty I have a transferable ext warr for car I have sold.

Auto extended warranty
I have a transferable ext warr for car I have sold. I mentioned it to the buyers as a selling point. They offered me 16000, $4000 less than asking price, and never asked about the warranty. I said 17000 was lowest I would go, again no mention of the warranty.

I gave them the title and bill of sale which states ”As Is” and they paid me $17000 (2004 GMC Envoy). After all the hand shaking was done, the man asked when I would be transferring the warranty, as that was a factor in the decision to buy the car. I said I would look into it and get back to them. I called the warranty co. and they tell me I can get a $900 refund. I am NOT going to give the buyer the warranty. Can I get in trouble? I am not a nasty person, but I had another offer for same price and no discussion of warranty. It is usually I that learn the hard way at others gain. This car was a good deal for them, and at least $3000 below book value. Also…they live in Mass and I am in RI…Please help!