NullPointerException with navigation component's argument with defaultValue

Question

I've encountered into a strange situation. Maybe someone has an idea why this can happen. I've added one argument to the MyActivity in main_graph.xml - isRecommended - with a default value (false):

<activity
    android:id="@+id/myActivity"
    android:name="com.mydomen.MyActivity"
    android:label="MyActivity"
    tools:layout="@layout/my_activity">
    <argument
        android:name="contentItems"
        app:argType="com.myActivity"
        android:name="com.mydomen.MyItem[]" />
    <argument
        android:name="myMetadata"
        android:defaultValue="@null"
        app:argType="com.mydomen.MyMetadata"
        app:nullable="true" />
    <argument
        android:name="isRecommended"
        android:defaultValue="false"
        app:argType="boolean" />
</activity>

and everything works fine, but one of my unit tests fails - namely, a NullPointerException is thrown in the test on the line with this verify:

@Test
fun `check onSomeMethodClicked`() {
    ...
    myViewModel.testAction()

    verify(exactly = 0) {
        navigationObserver.onChanged(
            NavigationCommand.To(
                MainGraphDirections.actionGlobalMyActivity(
                    listOf<MyItem>()
                )
            )
        )
    }
}


java.lang.NullPointerException
 at com.mydomen.MainGraphDirections$ActionGlobalMyActivity.getIsRecommended(MainGraphDirections.java:371)
 at com.mydomen.android.MainGraphDirections$ActionGlobalPlayerActivity.hashCode(MainGraphDirections.java:412)
 at com.mydomen.android.common.base.navigation.NavigationCommand$To.hashCode(NavigationCommand.kt)

While there is only one actionGlobalMyActivity method in the generated MainGraphDirections class:

  @NonNull
  public static ActionGlobalMyctivity actionGlobalMyActivity(@NonNull MyItem[] myItems) {
    return new ActionGlobalMyActivity(myItems);
  }

There are no methods that also take in isRecommended argument. So why is this exception thrown?..