Why can't I upgrade my adventurer to an adept?

[Chim66]

I have an adventurer with now 100 XP accumulated and I want him to upgrade to an adept/mage. The option "Upgrade unit (Adept)" is shown, but it is not active.

I do have a Mage Guild in the city and I have just researched Sorcery.

Why can't I upgrade my adventurer to an adept?

I play Elohim.

 

[A Moon]

Do you have enough money for the upgrade?

 

[Chim66]

You are right, stupid me.

Thank you!