The 18-year old Kenyan-born forward is in the first year of a two-year deal but has signed a two-year extension keeping him with the Reds until the end of the 2016/17 A-League season.
"I feel very happy with the decision we've made because it feels like a family at this club," said Mabil, who was born in a Kenyan refugee camp to Sudanese parents.
"To be offered a further two-year deal is really good for my development. Josep (Gombau) is a really good coach and I feel comfortable and I am learning a lot under him. I'm in a really good environment to learn and that's why I really enjoy it here."
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