The 24-year-old is back on the mend after a serious leg injury which kept him on the sidelines for the whole of last season.
Manager Graham Alexander told the club website: “It was extremely unfortunate for Jamma and ourselves when he got injured in the final game of last pre-season.
“He didn’t manage to play a single game in League One. He has missed a year of football which he is desperate to make up for.
“He has been working extremely hard on his rehabilitation and hopefully he will back with us for the start of this pre-season.
“It is like signing a new player again. He has been stop-start with injury throughout the past 18 months.
“We still feel there is a very good striker in Jamille who can score goals for us. This contract gives him the chance to realise his full potential with us. We look forward to having him back.”