Do not require Version=4.01 or OData-Version:4.01 for these new targets. Rationale: we already require in CSDL Version 4.0 Errata 03 that (minus the blue text) Unknown or invalid annotations should never result in an error, as long as the payload remains well-formed. Clients SHOULD ignore invalid or unknown terms and silently treat unexpected or invalid values (including invalid type, invalid literal expression, invalid targets, etc.) as an unknown value for the term. So worst case clients the annotation on the overload. Add the blue text to make this unambiguously clear.