RawFileBodyPart not found

I’m using Gatling version 2.3.0. I want to upload a Json file but the method RawFileBodyPart could not be found

.post(requestSpecification + "/upload")

I also tried bodyPart.rawFileBodyPart, but it's still not found. Do you have any idea why I get this error ?

Thank You

I imported io.gatling.http:

import io.gatling.http._

When I trye to define: 

HttpDsl is not found in the io.gatling.http package. But when I open the io.gatling.http package, I see the class and the method I need.
Do you have any idea why ?