He, along with another new signing - Carlos Edwards, had their first day of training today. It was also new coach, Neil Bailey's first day in the job.
Roy Keane said: "Jonny's here on loan until the end of the season. He came up last night and I'm delighted with him.
"He's been so enthusiastic since the moment I spoke to him and that's great, he can't wait to get started.
"He can play at left-back - he's played there for his country and enjoyed it - but I see him as a centre-half. I've gone down the road of playing lads out of position, I don't really want to go there again.
"It's good for him to be back in England and playing."