PropertyChanged event remains null after successful binding

Question

I have a UserControl named StatusIndicator, with a Dependecy Property on it, which has a PropertyChangedCallback I need, when the property changes to change Visual State.
I have a GameState class with a CurrentName property, which is bound to my UserControl's dependecy property. It implements INotifyPropertyChange as well, and contains these lines:

private static State current = State.Free;
public State Current {
  get { return current; }
  set { 
     current = value;
     CurrentName = current.ToString("G");
   }
}

private static string currentName = State.Free.ToString("G");
public string CurrentName {
  get { return currentName; }
  set {
     currentName = value;
     OnPropertyChanged("CurrentName");
   }
}

public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName) {
  PropertyChangedEventHandler handler = PropertyChanged;
  if (handler != null) {
    handler(this, new PropertyChangedEventArgs(propertyName));
  }
}

Unfortunatelly PropertyChanged is always null, and I am unable to use my callback. The statically initialized currentName value is set correctly, but later changes does not affect the view.

I use StatusIndicator in the MainWindow.xaml:

<Window x:Class="BattleHack.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:BattleHack.Managers"
    xmlns:ctrl="clr-namespace:BattleHack.Controls"
    xmlns:entity="clr-namespace:BattleHack.Entities"
    Title="BattleHack" Height="700" Width="500">

<Window.Resources>
        <entity:GameState x:Key="GameState" />
        <!-- ... -->    
</Window.Resources>
...
<DockPanel>
...
<ctrl:StatusIndicator Status="{Binding CurrentName, Source={StaticResource GameState}}" /> 
...
</DockPanel>

It is a project just to learn and try out things, but i would be glad if someone could help me.