I'm going to close this as "Won't fix". The reason being that the API should be able to create the same types of property paths as one could get from regular constraint validators and value extractors. There could be, although unlikely, a value extractor for a non-generic type which adds a path node (by passing a node name to the receiver), in which case ContainerElementNode#getTypeArgumentIndex() would return null. To allow for creation of such path via the builder API, the type argument index parameter should be able to receive null as a parameter, too.