The 20-year-old scored his second goal of the season in a 2-0 win over Crystal Palace on Saturday.
"We are in negotiation with his representatives and if I was the club I'd get it done as soon as possible," Sky Sports News quotes the Scottish coach as saying. "He's hungry and he wants to play.
"This contract is important but it's not the most important one he'll ever sign, that's further down the line. I think he is happy to work with me."
The England Under-21 international's current deal expires at the end of the season.