LONDON (AP) — Lawyers for WikiLeaks founder Julian Assange have requested permission to appeal a ruling that opened the door for his extradition from Britain to the United States on spying charges.

The attorneys on Thursday asked for permission to appeal the High Court’s ruling, arguing that the U.S. government’s pledge Assange wouldn’t be subjected to extreme conditions in prison was meaningless because it is conditional and could be changed at the discretion of American authorities.

Earlier this year, the U.S. State Department promised that if he is convicted Assange wouldn’t be imprisoned at the “supermax” penitentiary in Florence, Colorado, the highest-security prison in the country. They also pledged he wouldn’t be held under “special administrative measures,” which can include segregation from other prisoners and the loss of privileges such as visits, correspondence and use of the telephone.

Attorneys don’t know when the High Court will rule on the application, but they don’t expect a decision until the third week of January, Stella Moris, Assange’s fiancée, said in a statement.