Edited Issue: Null Reference on Loading File created by OpenXML [8631]

I've managed to create a very basic macro enabled spreadsheet via OpenXML (merging a VBA macro from another spreadsheet along the way).

The generated spreadsheet opens up correctly in Excel - the macro is present, together with the data I've put in there.

However, when I try to use ClosedXML to open the file, I get a "NullReferenceException was unhandled" error message appear.

Here's the code for opening the file:

var nwb = new XLWorkbook("C:\\Temp\\ExcelTest.xlsm");

I've attached the file.

Any help would be appreciated...