Combobox change size after the value is selected.

[Brovns]

Hi, I have an issue with the combobox size after picking the item.
Before I pick anything the size is normal:

After I pick any value the size is much bigger.

Here is the XAML

        <StackPanel Orientation="Horizontal" Grid.Column="0">
            <TextBlock Grid.Column="0" Text="Passed the test:" Width="auto" HorizontalAlignment="Center" VerticalAlignment="Center" Foreground="{DynamicResource TextFillColorPrimaryBrush}"/>
            <ComboBox Margin="5,0,0,0"
            ItemsSource="{Binding ValidationResults}"
                SelectedItem="{Binding SelectedResult}"
                Width="120">
                <ComboBox.ItemTemplate>
                    <DataTemplate DataType="model:ValidationResult">
                        <ListBoxItem Content="{Binding passedText}"/>
                    </DataTemplate>
                </ComboBox.ItemTemplate>
            </ComboBox>
        </StackPanel>

Can someone please help me with what I am doing wrong? This causes the whole program to look out of scale.

Thank you.

[Brovns]

I fixed this by changing listboxitem to TextBlock