How can I remove the black header that appears on my WPF DataGrid?

I am building this table on WPF .NET 8

<DataGrid x:Name="dataGrid"
      Width="640"
      ClipToBounds="True"
      AutoGenerateColumns="False"
      GridLinesVisibility="All"
      HeadersVisibility="Column"
      RowHeaderWidth="0"
      IsReadOnly="True"
      CanUserAddRows="False"
      CanUserDeleteRows="False"
      CanUserReorderColumns="False"
      CanUserResizeColumns="False"
      CanUserResizeRows="False"
      HorizontalScrollBarVisibility="Disabled"
      VerticalScrollBarVisibility="Auto"
      ScrollViewer.CanContentScroll="False"
      Background="Transparent"
      BorderThickness="1"
      EnableRowVirtualization="True"
      EnableColumnVirtualization="True"
      VirtualizingPanel.VirtualizationMode="Recycling">

<DataGrid.Resources>
    <!-- Light/dark theme-aware header style -->
    <Style x:Key="BaseHeaderStyle" TargetType="DataGridColumnHeader">
        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" />
        <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" />
        <Setter Property="FontWeight" Value="SemiBold" />
        <Setter Property="Padding" Value="5" />
    </Style>
</DataGrid.Resources>


<DataGrid.Columns>
    <DataGridTextColumn Binding="{Binding SourceType}" Header="Print Source" Width="200">
        <DataGridTextColumn.ElementStyle>
            <Style TargetType="TextBlock">
                <Setter Property="HorizontalAlignment" Value="Left" />
            </Style>
        </DataGridTextColumn.ElementStyle>
        <DataGridTextColumn.HeaderStyle>
            <Style TargetType="DataGridColumnHeader" BasedOn="{StaticResource BaseHeaderStyle}">
                <Setter Property="HorizontalContentAlignment" Value="Left" />
            </Style>
        </DataGridTextColumn.HeaderStyle>
    </DataGridTextColumn>

    <DataGridTextColumn Binding="{Binding PrintedAt}" Header="Printed At" Width="250" CanUserSort="False">
        <DataGridTextColumn.ElementStyle>
            <Style TargetType="TextBlock">
                <Setter Property="HorizontalAlignment" Value="Center" />
            </Style>
        </DataGridTextColumn.ElementStyle>
        <DataGridTextColumn.HeaderStyle>
            <Style TargetType="DataGridColumnHeader" BasedOn="{StaticResource BaseHeaderStyle}">
                <Setter Property="HorizontalContentAlignment" Value="Center" />
            </Style>
        </DataGridTextColumn.HeaderStyle>
    </DataGridTextColumn>

    <DataGridTextColumn Binding="{Binding PageCount}" Header="Pages Printed" Width="170">
        <DataGridTextColumn.ElementStyle>
            <Style TargetType="TextBlock">
                <Setter Property="HorizontalAlignment" Value="Right" />
            </Style>
        </DataGridTextColumn.ElementStyle>
        <DataGridTextColumn.HeaderStyle>
            <Style TargetType="DataGridColumnHeader" BasedOn="{StaticResource BaseHeaderStyle}">
                <Setter Property="HorizontalContentAlignment" Value="Right" />
            </Style>
        </DataGridTextColumn.HeaderStyle>
    </DataGridTextColumn>
</DataGrid.Columns>

The table is exactly how I want it to be, however there is a black extra header for some reason and I can't find out how to remove this. I don't want to put the DataGrid in a Border as this doesn't work I already tried that. Any ideas?

It currently looks like this: