How can you emprison the ruler of the Antigonid Kingdom as Thrace ?

[Ajax Telamônios]

If you take the last settlement of Antigonid Kingdom and choose to spare their ruler after choosing the victory conditions, the mission Poetic Justic stop to be available. And I don't see how can you emprison a leader without conquering all of their lands.

 

[Nostalgium]

Fairly certain you have to pick the "Imprison their leaders" after annexing them, not pass judgement on the individual families or spare them.

 

[Ajax Telamônios]

I just tried it, it doesn't work and Imprison their leaders doesn't imprison their ruler it seems. Maybe it is due to the fact that the Antigonid Kingdom name was changed to Asian Kingdom ? Or there is an other way to imprison him...

 

[Ajax Telamônios]

Did anyone else tried it ?