Can not build farms on hills?

[Ash_F]

From civ wiki: City ruins, roads, camps, and pastures have all been improved and you can now build farms on hills.

From the pdf manual: Generally, farms can be constructed in any tile that doesn’t contain a resource.

It seems I can only build farms on hills which are adjacent to rivers. I can farm a desert but not a grassland hill. Is this intentional? I hope not because the wording seems to suggest otherwise. It would make a lot of spots more viable for cities.

[norbak]

When building a farm on hill (in this example with trees as well) the tooltip also tells you that it gives you +1 production, which it doesn't.

[Ash_F]

When building a farm on hill (in this example with trees as well) the tooltip also tells you that it gives you +1 production, which it doesn't.

In that example was your hill next to a river?