SpringBoot: can't create fully executable jar with 2.0.0-M3

I have a multi module Gradle project and I tried to upgrade to 2.0.0-M3. Following the instructions here, I added this to my build script:

springBoot {
    executable = true
}

But when I build I get the following error:

Could not set unknown property 'executable' for object of type org.springframework.boot.gradle.dsl.SpringBootExtension.

Is it something broken in the milestone or am I doing something wrong?