Can't get SelectedValue in WinUI 3 ComboBox to work

I tried this with String (hstring) combo items and everything worked fine. Now I try to use structure and... trying to fill ComboBox and select one of them. ComboBox is filled ok, but no item is selected. I'd like to select them by Locale. What I do wrong? :)

Parts of source files here. IDL file:

    [default_interface]
    runtimeclass LanguageOpt
    {
        LanguageOpt();
        String Native;
        String Locale;
    };

    [default_interface]
    runtimeclass Settings : Microsoft.UI.Xaml.Controls.Page, Microsoft.UI.Xaml.Data.INotifyPropertyChanged
    {
        Settings();

        // UI languages
        Windows.Foundation.Collections.IObservableVector<LanguageOpt> Languages{ get; };
        LanguageOpt CurrentLang;
    }

Some code (.h):

    struct Settings : SettingsT<Settings>
    {
Windows::Foundation::Collections::IObservableVector<LanguageOpt> Languages();

        LanguageOpt CurrentLang();
        void CurrentLang(LanguageOpt const& value);


    private:

        LanguageOpt m_CurrentLang;
        Windows::Foundation::Collections::IObservableVector<LanguageOpt> m_Languages;
    };

.cpp file

    Settings::Settings()
    {
        m_Languages = winrt::single_threaded_observable_vector<LanguageOpt>();
        ... // filling m_Languages

        // set current language
        m_CurrentLang.Locale(L"en-US");
        m_CurrentLang.Native(L"English");
    }

XAML:

        <ComboBox x:Name="LanguageCombo"
                  ItemsSource="{x:Bind Languages}" 
                  SelectedValuePath="Locale"
                  SelectedValue="{x:Bind CurrentLang, Mode=TwoWay}">
            <ItemsControl.ItemTemplate>
                <DataTemplate x:DataType="local:LanguageOpt">
                    <TextBlock Text="{x:Bind Native}"/>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ComboBox>

When I try to check what's selected (after changing selection in running app) by calling CurrentLang(), I get the same value set in Settings constructor despite TwoWays mode. It looks like binding is not established :)

Finally I've found the solution.

Changes in IDL file:

1. runtimeclass LanguageOpt must be declared with BindableAttribute

    [Windows.UI.Xaml.Data.Bindable]
    runtimeclass LanguageOpt
    {
        LanguageOpt();
        String Native {get;};
        String Locale {get;};
    };

2. LanguageOpt CurrentLang must be changed to

    IInspectable CurrentLang;

I hope this will help to anybody who will encounter the same problem :)