Splashscreen API not showing icon

We are currently implementing a splashscreen via the new Splashscreen API. We are following the migration guide. The background color is set correctly (by windowSplashScreenBackground), but the icon is not visible, neither on an Emulator, nor on a physical device.

build.gradle

android {
    compileSdkVersion 31
    ...
}

dependencies {
    implementation "androidx.core:core-splashscreen:1.0.0-alpha01"
    ...
}

values-v31/themes.xml

<style name="AppTheme" parent="Theme.SplashScreen">
    <item name="postSplashScreenTheme">@style/AppThemeCompat</item>
    <item name="windowSplashScreenBackground">@android:color/black</item>
    <item name="windowSplashScreenAnimatedIcon">@mipmap/ic_launcher</item>
    <item name="windowSplashScreenAnimationDuration">200</item>
</style>

AndroidManifest.xml

<application
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme">
    ...
</application>

MainActivity.kt

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen()
    ...
}