Error: 'Microsoft.XLANGs.BaseTypes.BPELExportable': inconsistent duplicate module attribute

While working on a solution we suddenly encountered the following error message while trying to build the code.

'Microsoft.XLANGs.BaseTypes.BPELExportable': inconsistent duplicate module attribute

It can be a nuisance to find the problem if you don't work with BizTalks BPEL capabilities that often. It is however quite easy to fix. The error message is due to one orchestration having a different Module Exportable setting than the other orchestrations in the project. Making sure that the setting match between all orchestrations will make the error message disappear.