WPF combobox hardcodes the textbox background to white

[KirillOsenkov]

            <Border x:Name="Border"
                Margin="{TemplateBinding BorderThickness}"
                Background="{StaticResource &#271;}">
                <TextBox x:Name="PART_EditableTextBox"
                    Style="{StaticResource &#240;}"
                    IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}"
                    Margin="{TemplateBinding Padding}"
                    HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                    VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
            </Border>