Intellij can not resolve Symbol in Gradle Project with multiple SourceSets

I am working on a Gradle Project that uses multiple Sourcesets to build different WARs.

Everything works fine from command line. Gradle builds the WARs correctly. But in IntelliJ it says for every *.java file under src/k that it can not resolve the dependencies from src/main.

I tried to fix it by adding the directories as SourceDirs using the idea-gradle plug in but that did not work, unfortenetly.

plugins {
    id 'org.gretty' version '2.2.0'
    id 'war'
    id 'idea'
}

configurations {
    kCompile.extendsFrom compile
    kRuntime.extendsFrom runtime
}

sourceSets {
    main {}        
    k {
        java {
            compileClasspath += main.output
            runtimeClasspath += main.output   
            srcDirs = ['src/main/java', 'src/k/java/']
        }

        resources { 
            compileClasspath += main.output
            runtimeClasspath += main.output
            srcDirs = ['src/main/resources', 'src/k/resources']
        }
        output.resourcesDir = 'build/resources/main'
        output.classesDir = 'build/classes/java/main'
    }  
}

idea {
    module {
        sourceDirs += file('src/main/java')
        sourceDirs += file('src/k/java')
        downloadJavadoc = true
        downloadSources = false
    }    
}

repositories {
    mavenCentral()
    jcenter()
}

gretty {
    servletContainer = 'tomcat85'
}

dependencies {
    ...
}

task kWar(type: War) {
    appendix = "k"
    from sourceSets.k.output
}


farm {
    webapp "build/libs/App-k.war", contextPath: '/k'
}

project.afterEvaluate {
    farmRunWar.dependsOn kWar
    farmRunWar.shouldRunAfter kWar

}

I found a fix where I had to add the dependency for main manually to k in Intellij via File > Project Structure > App_k > + > module dependency > App_main > ok. Is there a way to tell Intellij to do this with the idea gradle-plug-in ?