R – Problem with Binding Dependency Property on a UserControl

I have a two userControls (IconUserControl & DisplayUserControl), I'm having a problem with binding dependency properties, here's some detail:

• IconUserControl has a bool DP of IsDisplayShown
• DisplayUserControl has a bool DP of IsDisplayShown

In the XAML I have:

<local:DisplayUserControl
                    x:Name="DisplayUserControl"
                    IsDisplayShown="{Binding ElementName=IconUserControl, Path=IsDisplayShown, Converter={StaticResource DummyConverter}}" />

<local:IconUserControl
                    x:Name="IconUserControl" />

When IconUserControl.IsDisplayShown is set to true, I can see in the DummyConverter this value getting passed, but it never sets DisplayUserControl.IsDisplayShown.

However, if in the codebehind for the View I set DisplayUserControl.IsDisplayShown = true;, then it works fine.

I have the DataContext for both UserControls set to "this" in the constructor. I've tried to fiddle with the "Mode" property of the binding.

*Note: DummyConverter just returns the value, I only have this to confirm that the Binding is trying to work.

What am I doing wrong?

Edit:

Here's the two DPs:

public bool IsDisplayShown
        {
            get { return (bool)GetValue(IsDisplayShownProperty); }
            set { SetValue(IsDisplayShownProperty, value); }
        }
        public static readonly DependencyProperty IsDisplayShownProperty =
            DependencyProperty.Register("IsDisplayShown", typeof(bool), typeof(IconUserControl), new UIPropertyMetadata(false));

public bool IsDisplayShown
        {
            get { return (bool)GetValue(IsDisplayShownProperty); }
            set
            {
                if (value)
                    ShowOpenItems();
                else
                    HideOpenItems();
                SetValue(IsDisplayShownProperty, value);
            }
        }
        public static readonly DependencyProperty IsDisplayShownProperty=
            DependencyProperty.Register("IsDisplayShown", typeof(bool), typeof(DisplayUserControl), new UIPropertyMetadata(false));