Plugin version is not the same as library version

Go to Intellij Preferences -> Build, Execution, Deployment -> Kotlin Compiler. Update Language version and Api version to the one you wish . This should be the accepted answer.

This time I helped myself with the following:

You can check the Kotlin version in Tools | Kotlin | Configure Kotlin Plugin Updates . If you have projects created with earlier Kotlin versions, change the Kotlin version in your projects and update kotlinx libraries if necessary – check the recommended versions.