With a crusade, Ninoslav was baptized, only to abjure Christianity in 1233.
He was asked whether certain books had been written by him and whether he was prepared to maintain or to abjure what he had written.
At the council of Pisa, where he was compelled to abjure his errors and was sentenced to imprisonment.
Among the propositions he could heartily abjure was that relating to transubstantiation; among those he felt constrained unflinchingly to maintain was one which had given great offence, to the effect that Christ, not Peter, is the head of the church to whom ultimate appeal must be made.
The final judgment found no proof of heresy, but compelled him to abjure sixteen errors, rather extorted than extracted from his writings, suspended him from his see for five years, and secluded him to the Dominican cloister of Sta Maria sopra Minerva.