Autoform suddenly stopped handling booleans

I have an old system, predating the dinosaurs and even daylight, that was running Meteor 1.x until I upgraded it up to 2.15 last week. I had to remove/update a lot of components but now it is running well. Apart from Booleans in Autoform.

The booleans display as they should, but they handle as if they are strings so Autoforms validator complains, saying it has to be a value there, regardless if it is checked or not.

Versions for what I see is the stuff related are the same as when sys was running 1.x:

aldeed:autoform@5.8.1
aldeed:collection2@2.10.0
aldeed:collection2-core@1.2.0
aldeed:schema-deny@1.1.0
aldeed:schema-index@1.1.1
aldeed:simple-schema@1.5.4
aldeed:template-extension@4.1.0

Anyone has a clue why this is happening?

Thanks