IDEA showing a project twice in tree

I have a Kotlin project with Gradle that has two children. Whenever I try to open it in IDEA, one of the children is shown twice in the tree.

In the tree, you can see two projects at top level, grpc and grp. The issue is that grpc (from top level) is the same project as the grpc that's a children of grp.

Here are my Gradle build files:

The parent gradle.build:

buildscript {
    ext.kotlin_version = '1.0.1'
    repositories {
        jcenter()
        mavenCentral()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

allprojects {
    repositories {
        jcenter()
        mavenCentral()
    }
} 

The gradle.settings file:

include ':grpstd', ':grpc'

The grpc gradle.build:

apply plugin: 'antlr'
apply plugin: 'application'
apply plugin: 'kotlin'

mainClassName = 'sron.grpc.MainKt'

compileKotlin.dependsOn generateGrammarSource

generateGrammarSource {
    arguments += ['-package', 'sron.grpc.compiler.internal']
}

dependencies {
    antlr 'org.antlr:antlr4:4.5.2-1'

    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    compile 'commons-cli:commons-cli:1.3.1'
    compile 'org.ow2.asm:asm:5.0.4'
    compile project(':grpstd')

    testCompile 'junit:junit:4.12'
    testCompile "org.jetbrains.kotlin:kotlin-test:$kotlin_version"
}

The grpstd gradle.build:

apply plugin: 'kotlin'

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"

    testCompile 'junit:junit:4.12'
    testCompile "org.jetbrains.kotlin:kotlin-test:$kotlin_version"
}

Why is that project being shown twice? How can I prevent it?