Upgrade from 3.8.1.0 to 3.9.1.0 breaks code

If I upgrade from 3.8.1.0 to 3.9.1.0 part of my code breaks:

Fx:

Friend MustOverride Function Execute() As Excel

I get a "Type is not defined" blue error line under Excel

Are there breaking changes in 3.9.1.0 or am I not using the control correctly?

For some external reasons, class Excel is changed to Workbook since v3.9. So please change your code to:

Friend MustOverride Function Execute() As Workbook