Свързване към прикачено свойство в ControlTemplate - Silverlight

Имам този стил:

 <Style x:Key="ButtonStyle" TargetType="Button">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Grid>
                                        <StackPanel>
                           <Image Source="{Binding Path=local:AttachedProperties.Image}"  Stretch="None" HorizontalAlignment="Center" Margin="0" VerticalAlignment="Top"/>
                                <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                            </StackPanel>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

Проблемът е, че обвързването не работи за бутон:

<Button HorizontalAlignment="Center" Style="{StaticResource ButtonStyle}" VerticalAlignment="Center" Content="Button" local:AttachedProperties.Image="../Images/UserChart.png" Grid.RowSpan="2"/>

Какво правя грешно?