Cannot use native jsonnet support

I am trying to use native jsonnet support by enabling ```

and setting jsonnet file name in the UI.

But I get ````
linter: invalid or missing image`

Jsonnet file:

Manually convertedto yaml file is building fine:

Could you help?


Also I don get what is the relation between DRONE_JSONNET_ENABLED and jsonet extension, do I have to use them together?