Exception on onCreatePreferences, ParameterIsNotNull, parameter savedInstanceState

I took the code from the Android Doc, but the Activity crashes, stating:

E/AndroidRuntime: FATAL EXCEPTION: main Process: nl.cccccccccc.ttandroid.ddddddddd, PID: 19352 java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState at nl.cccccccccc.ttandroid.ddddddddd.SettingsActivity$MySettingsFragment.onCreatePreferences(Unknown Source:24) at android.support.v7.preference.PreferenceFragmentCompat.onCreate(PreferenceFragmentCompat.java:228) at android.support.v4.app.Fragment.performCreate(Fragment.java:2414)

class SettingsActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_settings)
        setSupportActionBar(toolbar)
        supportActionBar?.setDisplayHomeAsUpEnabled(true)

        this.supportFragmentManager
            .beginTransaction()
            .replace(R.id.settings_content, MySettingsFragment())
            .commit()
    }

    class MySettingsFragment : PreferenceFragmentCompat() {
        override fun onCreatePreferences(savedInstanceState: Bundle, rootKey: String) {
            setPreferencesFromResource(R.xml.pref_settings, rootKey)
        }
    }
}

Can someone give me a hint?