He has subsequently been linked with a move to Reading, Nottingham Forest and Ipswich when his current deal expires at the end of the season.
Swindon manager Danny Wilson said: "We have spoken to him about it and we are more than happy for him to stay.
"It was important that Charlie understood we are delighted with his progress.
"We have a clause in his contract which suggests that he will stay anyway and we just have to trigger it.
"We didn't want to leave him out on a limb at the end of the season."
Source: Team Talk