Created Unassigned: Problem with merging cells [15170]

I've a problem with merging cells. I use code like this
```
package.Workbook.Worksheets[1].Cells[30 + index, 1].Value = product.Label;
package.Workbook.Worksheets[1].Cells[30 + index, 1, 30 + index, 10].Merge = true;
```
But after saving documents and reopening it via Excel I'm getting error that file is corrupted and I can try restore it. After this excel shows message that action merging cells was deleted. But document still contain merged cells.
> Deleted records: Merging cells from part /xl/worksheets/sheet1.xml