Roughness mask - ERROR

[Slavq]

I’m trying to have different roughness on certain parts of my model, so wood would be dull, and metal more shiny (it’s an axe model in my case) - I’ve read that to achieve this, i need to use my specular map as the alpha of a Lerp node and set two roughness values that will set the reflective-rough surfaces depending on the specular map.
So i did this, and it gives me an error:

What i’m doing wrong here?

[Jacky]

Lerp Alpha accepts single channel only, so you need to plug red, green or blue channel of that mask texture.

[Slavq]

Thanks, it worked