How to use variables in a top-level gradle.properties file?

Gradle v2.9.x (old I know, but that’s another project)

I tried the solution suggested in gradle: how to access the gradle.properties from another project to no avail.

I want to define artifact versions on a top-level gradle.properties file like so

toplevel/gradle.properties file:
artifact1_version='1.0.0'

Then I want to be able to use the above variable in artifact1_version variable like so

toplevel/artifact1/gradle.properties file:
version="$artifact1_version"

Is this possible to do in Gradle? If so how?