Problem selecting listboxitems with mouse when stackpanel is Orientation=Horizontal

Question

In the listbox below, when I mouse over the item labeled "This does not work", I need to actually select the textblock in order to get the listboxitem to select. In the one labeled "This works" the only difference is that the Orientation is not set to horizontal. In the one that works, I can select all the way to the right of the textblock and the listboxitem will be selected. I need Orientation set to horizontal because I am putting an image and then the textblock in the listboxitem.

                <ListBox Name="theListBox"

HorizontalAlignment="Stretch" >

                    <ListBoxItem Content="ListBoxItem2"/>
                    <ListBoxItem HorizontalAlignment="Stretch" HorizontalContentAlignment="Stretch">
                        <StackPanel>
                            <TextBlock Text="This works"></TextBlock>
                        </StackPanel>
                    </ListBoxItem>
                    <ListBoxItem HorizontalAlignment="Stretch" HorizontalContentAlignment="Stretch">
                        <StackPanel Orientation="Horizontal">
                            <TextBlock Text="This does not work"></TextBlock>
                        </StackPanel>
                    </ListBoxItem>