VS2012, vspackage: Type exists in two .net assemblies

How to get around this error message? Copy the type to my own sourcecode?
Pacakage is initially created in VS 2012
I can't remove the reference as the project will not compile if i do

Error message:

Microsoft.VisualStudio.VSConstants.GUID_ItemType_PhysicalFile
The type 'Microsoft.VisualStudio.VSConstants' exists in both
'Microsoft.VisualStudio.Shell.11.0.dll' and 
'Microsoft.VisualStudio.Shell.dll'

Thanks  /Peter