Spacetime filling branes in string theory are consistent only if a suitable truncation takes place. This is well known in type IIB, where D9 branes can be inserted only after performing an 'orientifold' projection, and this leads to type-I superstring theory. We show that supersymmetry of type-IIB also allows the presence of a different type of spacetime filling 9-brane, that is not a D9-brane. We argue that this brane can only be consistently introduced if a truncation of type-IIB superstring is performed. We finally discuss some possible physical implications.