When I try do perform this operation, I have a error. What's wrong?

alter table DIARIO
add constraint FK_DIARIO_DISCIPLINA_PROFESSOR foreign key
(ID_DISCIPLINA,ID_PROFESSOR)
references LECIONAR(ID_DISCIPLINA,ID_PARCEIRO);


Operation Completed - There Were Errors
ISC ERROR CODE:335544351

ISC ERROR MESSAGE:
unsuccessful metadata update
could not find UNIQUE INDEX with specified columns