Custom scripts in kotlin dsl

Question

I am trying to break my big build.gradle.kts file and use

apply(from=script1.gradle.kts)
apply(from=rpm.gradle.kts)

My rpm-gradle.kts looks like

import com.netflix.gradle.plugins.rpm.Rpm
val buildRpmTask2  by tasks.registering(Rpm::class) {
  os = org.redline_rpm.header.Os.LINUX
  packageName="app"
  release = "1"
  user = "root"
  packageGroup = "root"
}

However, my Intellij is not doing syntax highlighting and my gradle build is failing while complaining that RPM can not be found. Should I use BuildSrc instead ?