Height setter ignored on custom Window - wpf

Question

I added a Custom Control to my project and changed the parent type to Window. I show it on a button click.
I have style setters for height and width, but only the one defined first in the xaml has effect. The other shows larger than styled.
Anyone know what's happening here?
In generic.xaml:
<Style TargetType="{x:Type local:ChildWindow}">
<Setter Property="Width" Value="300"/>
<Setter Property="Height" Value="300"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type local:ChildWindow}">
<TextBlock Background="White">Child window</TextBlock>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
ChildWindow.cs is default except the parent is now "Window":
public class ChildWindow : Window
{
static ChildWindow()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(ChildWindow), new FrameworkPropertyMetadata(typeof(ChildWindow)));
}
}
MainWindow.xaml.cs shows the ChildWindow:
private void Button_Click(object sender, RoutedEventArgs e)
{
var childWindow = new ChildWindow();
childWindow.Show();
}

Answer 1

Workaround:
I haven't found why it behaves like that, or how to make the style setters work, but a workaround is to get rid of the style setters and set the default values for the Width and Height dependency properties. I did this in the static constructor:
static ChildWindow()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(ChildWindow), new FrameworkPropertyMetadata(typeof(ChildWindow)));
// Get rid of the style setters and add this:
WidthProperty.OverrideMetadata(typeof(ChildWindow), new FrameworkPropertyMetadata(300.0));
HeightProperty.OverrideMetadata(typeof(ChildWindow), new FrameworkPropertyMetadata(300.0));
}