Using spring-boot Gradle plugin but getting spring boot version from dependency management

Question

I have a Gradle setup where I currently need to hard code the spring-boot version. Is it possible to do this with dependency management instead? The issue occurs in my project module that contains the actual code. There I need a call to :

springBoot {
    requiresUnpack = ["com.example:util"]
}

In order to do that I need to apply the spring-boot plugin. For that plugin to be available I need to have a dependency to "org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}". And for that I need to specify the springBootVersion hard coded...

This is my parent gradle file:

buildscript {

    ext {
        springBootVersion = '1.4.0.RELEASE'
    }
    repositories {
        mavenCentral()
        jcenter()
    }
    dependencies {
        classpath "org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}"
        classpath 'io.spring.gradle:dependency-management-plugin:0.6.0.RELEASE'
    }
}

plugins {
    id "io.spring.dependency-management" version "0.6.0.RELEASE"
}

group 'test'


repositories {
    mavenCentral()
}

allprojects {
    apply plugin: 'java'
    apply plugin: 'io.spring.dependency-management'

    dependencyManagement {
        imports {
            // Note that these two BOM's are not always easy to combine, always define cloud first and try to find versions with same version of spring-boot when upgrading.
            mavenBom 'org.springframework.cloud:spring-cloud-starter-parent:Brixton.SR5'
            mavenBom 'io.spring.platform:platform-bom:2.0.7.RELEASE'

        }
    }
}

and this is my module gradle file:

group = "test"

apply plugin: 'spring-boot'
apply plugin: 'io.spring.dependency-management'

sourceCompatibility = 1.8
targetCompatibility = 1.8

// Temporary fix for jersey
springBoot {
    requiresUnpack = ["com.example:util"]
}

If I remove the dependency to spring-boot-gradle-plugin in parent gradle file, then I cannot use the apply plugin: 'spring-boot' in the module gradle file and without that the gradle DLS method springBoot { is not defined...

Can I achieve this without having to hard code springBootVersion = '1.4.0.RELEASE'in my parent gradle file?