"Problem loading widget" when using custom color attributes

We developing home screen widgets in 2021 and I tried to implement dark theme support.

According to https://developer.android.com/guide/topics/ui/look-and-feel/darktheme#widgets

"... use appropriate theme attributes instead of hardcoded colors."

So as I understand I can use custom attributes and I added attrs.xml in values folder

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <attr name="customBackgroundColor" format="color" />
</resources>

After that I added my custom attribute to light/dark theme

values/themes.xml

<resources>
    <style name="AppTheme" parent="Theme.MaterialComponents.Light">
        <item name="customBackgroundColor">@color/white</item>
    </style>
</resources>

And also for dark

values-night/themes.xml

<resources>

    <style name="AppTheme" parent="Theme.MaterialComponents">
        <item name="customBackgroundColor">@color/black</item>
    </style>
</resources>

Here is my widget layout:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="?attr/customBackgroundColor" />

When I placing widget on home screen I got "Problem loading widget" message.

When I tried to hardcode colors for layouts, everything works as expected.

I also tried using default attributes "colorPrimary" and there was no error message but widget not changing color according to theme I switched.

Do I missing something or information in official docs is incorrect?