Can a worker NOT build a farm?

Can a civ-specific worker unit not be able to build a farm? If so, how do I update it so that it can't build a specific improvement?

Thanks guys!

Assuming the civ-specific worker unit is a UU, you'll have to define which improvements they can build under Unit_Builds. You can simply leave out the BUILD_FARM BuildType.

As bouncymischa said. It's essentially the reverse of how you can make trireme replacements be able to cross oceans: counter-intuitively, by not giving them the anti-promotion that prevents ocean crossing. Units can, after all, only do what you specifically allow them to.

Thanks so much, guys!