SettingsPropertyValue in ConfigurationManager won't serialize array of strings

Question

I'm transferring an application from .Net Framework 4.6.2 to .NET 6 and I'm getting some problems with the ConfigurationManger where it is not able to serialize an array of strings. Is this intended behvaiour? How should I circumvent this?

This is an example of the problem:

using System.Configuration;

var attributes = new SettingsAttributeDictionary();
var attr = new UserScopedSettingAttribute();
attributes.Add(attr.TypeId, attr);

var value = new[] {"test"};

var provider = new LocalFileSettingsProvider();
var prop = new SettingsProperty(
    "testName",
    typeof(string[]),
    provider,
    false,
    default(string[]),
    SettingsSerializeAs.Xml,
    attributes,
    false,
    false);

var val = new SettingsPropertyValue(prop);
val.PropertyValue = value;

if (val.SerializedValue == null)
{
    Console.Write("Not serialized");
}