Difficulty moving Gradle configuration to an external script

I am trying to move some parts of my Gradle build script to an external configuration file that can be shared among projects. Here is an example with the Detekt plugin:

Current Code

build.gradle.kts (condensed to only the relevant parts)

plugins{
    id("io.gitlab.arturbosch.detekt").version("1.19.0-RC1")
}
...
detekt{
   ...
}

What I'm trying to do

build.gradle.kts

apply(File("common.gradle.kts"))

common.gradle.kts

plugins {
    id("io.gitlab.arturbosch.detekt").version("1.19.0-RC1")
}

detekt{
   ...
}

but when I do this I get this error:

<my_project>\common.gradle.kts:7:1: Unresolved reference: detekt

So the plugin section doesn't appear to be doing anything. And just to be clear, this plugin does not need anything in dependencies section, it works fine inside build.gradle.kts with only the plugin declaration.

Why doesn't this work?