How to add ScrollViewer to ItemsControl

Question

<ScrollViewer VerticalScrollBarVisibility="Visible">
    <ItemsControl ItemsSource="{Binding SelectedItem.Episodes, Mode=OneWay}" 
         MaxHeight="180"
         AlternationCount="1000">
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <TextBlock>
                  <Hyperlink NavigateUri="{Binding Path=DataContext.SelectedItem.EpisodeUrls[0], 
                               RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" 
                                    Foreground="White" 
                                    RequestNavigate="HyperlinkRequestNavigate">
                            <TextBlock Text="{Binding}" />
                        </Hyperlink>
                    </TextBlock>
                </StackPanel>
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</ScrollViewer>

This is my xaml. I need scrolling for my EpisodeUrls elements. The scroll has been added, but the scroll slider itself is missing. Everything is fine with the horizontal line, everything is displayed, but with the vertical line there is a problem. Can someone help please?