Mobigen Sans-serif generic family in mobigen generated .mobi files

Hi everyone.

I am working on a book that needs to have some of its sections displayed in sans-serif font.

I have set the following rule for these kind of sections; nice and generic.
{font-family: sans-serif;}
The epub version of the book works as intended.

When I preview the file in the Kindle Previewer, however, everything is in serif font (except for some other parts of the book, that needed to be in monospace({font-family: monospace;}) , which are, curiously, displaying correctly)

What is the deal with kindlegen generated .mobi files and the sans-serif font family?
Do they simply not work or is there some trick to make the kindlegen not disregard the CSS rule when it compiles the book from .epub?

.mobi files in question are generated using the up-to-date Kindle Previewer's built in kindlegen functionality.

Thanks