Problem with text wrapping

Question

I have ListBox

            <ListBox Name="SettingsList"
                     ItemTemplate="{StaticResource SettingsItemTemplate}"
                     ItemContainerStyle="{StaticResource ListBoxItemStyle}"
                     />

and templates for them

        <DataTemplate x:Key="SettingsItemTemplate">
            <StackPanel Orientation="Horizontal"
                        Visibility="{Binding Visibility}"
                        toolkit:TiltEffect.IsTiltEnabled="True"
                        Tap="SettingsItem_Tap"
                        Margin="12,6,6,6"
                        >
                <Image x:Name="IconImage"
                       Source="{Binding Image}"
                       />
                <StackPanel Orientation="Vertical"
                        >
                    <TextBlock x:Name="TitleTextBlock"
                               Text="{Binding Name}"
                               Style="{StaticResource PhoneTextLargeStyle}"
                               />
                    <TextBlock x:Name="DescriptionTextBlock"
                           Text="{Binding Description}"
                           Style="{StaticResource PhoneTextSubtleStyle}"
                           TextWrapping="Wrap"
                           />
                </StackPanel>
            </StackPanel>
        </DataTemplate>

    <Style x:Key="ListBoxItemStyle" TargetType="ListBoxItem">
        <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
    </Style>

ItemsSource is setting in code-behind

            List list = new List();
            list.Add(new BuyApplicationSettingsItem());
            list.Add(new InterfaceSettingsItem() { BasePage = this });
            list.Add(new ApplicationSettingsItem() { BasePage = this });
            list.Add(new DataManagementSettingsItem() { BasePage = this });
            list.Add(new RateApplicationSettingsItem());
            list.Add(new FeedbackSettingsItem());
            list.Add(new AboutSettingsItem() { BasePage = this });
            //
            SettingsList.ItemsSource = list;

The problem is no text wrapping in Description field, so a part of text can not be readed. What is wrong?