View source of Kotlin package in Eclipse

Dear guru,

I am using package written in Kotlin (OkHttp) in my Java project in Eclipse. This package has sources jar attached. When I want to look at the sources (following up some method link, etc) I expect that Eclipse will show me that source as Kotlin one (I have Kotlin plugin installed) but I see it as a Java source without ability even to navigate to methods in Outline view … Is it possible to solve that problem somehow?

Thanks in advance,