The Converter class, in the eponymous example, had a null member variable that wasn't a nullptr - it pointed to an instance of NullConverter - so that other converters could test whether a Converter * they'd been passed was null (in the sense of pointing to a NullConverter). This, however, was susceptible to misreading - I misread one such comparison as a nullptr check and thus thought it redundant with an earlier actual nullptr check. To spare future readers similar confusion, replace the public static member variable with a protected (since only other derived classes need it) static predicate, to at least give the reader a clue that this is using the word null in a class-specific sense. Pick-to: 6.6 6.5 Task-number: QTBUG-111228 Change-Id: I1e4f494b303d1bf90107f8c6fa3a4a22f6d81b90 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>