WPF: How to style TextBlock of DataGridExtension ColumnHeader

In some DataGrids I have set some Columns to a fixed width and enabled textwrapping in the column header using a custom Style for the columnHeader:

            <Style TargetType="{x:Type DataGridColumnHeader}" x:Key="TextColumnHeaderWrap">
                <Setter Property="ContentTemplate">
                    <Setter.Value>
                        <DataTemplate>
                            <TextBlock TextWrapping="Wrap"
                                       Text="{Binding}"></TextBlock>
                        </DataTemplate>
                    </Setter.Value>
                </Setter>
            </Style>

I am now using the DataGridExtension-library (https://github.com/dotnet/DataGridExtensions) to add filter functionality. Unfortunately, this disables the textwrapping for the column headers! Here's a screenshot of the visual tree for a column with filter and one without:

How do I need to change the style so the textblock will wrap for a column with filter? thanks in advance!