PlDoc variables for polypmorphic types

Hi,
After a recent upgrade of SWI, PlDoc has started complaining about
variables in my type declarations. I have been using variables to represent
polymorphic types, for example, a hypothetical cons/3 predicate might
look like this

%% cons( ?Head:A, ?Tail:list(A), ?Whole:list(A)) is det.
cons(X,Y,[X|Y]).

However, PlDoc doesn't like my 'A' for the type of Head. The
'list(A)' is fine. It's good that PlDoc is checking the syntax more
thoroughly, but can we make it so that a variable can be a legal type?

Samer.