Possible to play vs. AI with custom 40 card decks?

[go1111111]

I'd like to be able to play against the AI using a custom 40 card deck (usually from a cube I recently drafted), and make the AI use another custom 40 card deck. I can create 40 card decks in the deck editor, which show up in the "Custom User Decks" dropdown in the constructed menu. However when I try to play with one of these decks or assign one to the AI, I get the error "<Player>'s deck should have at least 60 cards".

How can I disable this error / somehow play vs. the AI with custom 40 card decks? I assume there must be a way since some of the pre-constructed decks have 40 cards.

[friarsol]

Disable deck conformance in preferences