XLSX Export with no background color

[Aleksandar]

When exporting a report using the XLSX format, it always sets a white background and the gridlines aren't visible. I've set all the report, sections, and items to transparent background color. I've enabled "ShowGridlines" in runtime settings. When I export to XLS it works as expected with no background color. Therefore, I don't think it's an issue with the report itself. How can I export to XLSX with a transparent background to see the gridlines?