It could be that your default format doesn't match the file extension. You should specify the file format along with the filename, making sure the format matches the extension:
With someWorkbook
.SaveAs "C:\someDirector\Awesome.xlsm", fileformat:=xlOpenXMLWorkbookMacroEnabled
End With
OTOH, I don't see an extension on your .SaveAs filename. Maybe you need to supply one when doing this programmatically. That makes sense--not having to supply an extension from the GUI interface is convenient, but we programmers are expected to write unambiguous code. I suggest adding the extension and the matching format. See this msdn page for a list of file formats. To be honest, I don't recognize a lot o the descripions.
xlExcel8 = 56 is the .xls format
xlExcel12 = 50 is the .xlsb format
xlOpenXMLWorkbook = 51 is the .xlsx format
xlOpenXMLWorkbookMacroEnabled = 52 is the .xlsm format
xlWorkbookDefault is also listed with a value of 51, which puzzles me since I thought the default format could be changed.