Shouldnt params replace values marked with ':'?

[JulianWogersien]

I have this piece of code

However This results in this error

What exactly is wrong here? Afaik i did it like the example in the docs

[blackbeam]

Hi.

The naming rules was overlooked:

• parameter name must start with either _ or a..z
• parameter name may continue with _, a..z and 0..9