Force textblock to wrap in WPF listbox

<ListBox HorizontalContentAlignment="Stretch"  ItemsSource="{Binding Path=FriendsTimeline}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <Border BorderBrush="DarkBlue" BorderThickness="3" CornerRadius="2" Margin="3" >
                            <Image Height="32" Width="32"  Source="{Binding Path=User.ProfileImageUrl}"/>
                        </Border>
                        <StackPanel Orientation="Vertical">
                            <TextBlock Text="{Binding Path=User.UserName}"/>
                            <TextBlock Text="{Binding Path=Text}" TextWrapping="WrapWithOverflow"/> <!-- This is the textblock I'm having issues with. -->
                        </StackPanel>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>