Coppie di Michelson non confrontabili

Quandoprovo a digitareil seguente script di Michelson,ottengo unerrore ditipo.

 parameter unit;
storage (big_map (pair string address) (list timestamp));
code {CDR; NIL operation; PAIR};
 

 Ill formed type.
At line 2 characters 17 to 37,
comparable type expected.Type pair string address is not comparable.
 

Secondoil riferimento Michelson ,i tipi pair ty1 ty2,addresse string sono comparabili.Mi stoperdendo qualcosa?C'è unmodoper aggirare questoproblema?

When I try to type the following Michelson script, I get a type error.

parameter unit;
storage (big_map (pair string address) (list timestamp));
code {CDR; NIL operation; PAIR};

Ill formed type.
At line 2 characters 17 to 37,
comparable type expected.Type pair string address is not comparable.

According to the Michelson reference, types pair ty1 ty2, address, and string are comparable. Am I missing something? Is there are way to circumvent this issue?