.Net Settings file, complex types and serialization

I have the following types

[Serializable, XmlType(Namespace="http://mycompany/foo"]
public sealed class Limit
{
    [XmlElement(ElementName="Value1")]
    public double Value1 {get;set;}

    [XmlElement(ElementName="ComplexValue1")]
    public ComplexValue ComplexValue1 {get;set;}
}

[Serializable, XmlType(Namespace="http://mycompany/foo"]
public sealed class ComplexValue 
{
    [XmlElement(ElementName="Item1")]
    public double Item1 {get;set;}

    [XmlElement(ElementName="Item2")]
    public double Item2 {get;set;}
}

which I want to serialize to a .settings file.

When I copy the blob below into the settings file, I lose the ComplexValue1 element somehow:

<?xml version="1.0" encoding="utf-16"?>
<Limit>
  <Value1>20</Value1>
  <ComplexValue1>
     <Item1>2.0</Item1>
     <Item2>5.0</Item2>
  </ComplexValue1>
</Limit>

i.e. Visual Studio transforms it to:

<?xml version="1.0" encoding="utf-16"?>
<Limit>
<Value1>20</Value1>
</Limit>

with a bunch of namespaces that I think don't matter for the question...

What am I missing?