The England international has been linked with Manchester City and Benfica among others following his impressive displays, particularly in the Champions League.
"We received no bids for Fraser in the January window," the Celtic boss is quoted as saying in the Daily Mail.
"I think there will be something in the summer for him but he seems happy here and content. I wouldn't be surprised if something happens in the summer or we get offers then."
Forster joined Celtic for £2m from Newcastle United in 2012 following two successful loan spells at Parkhead.