In an attempt to agree with the truth-value assignments that are usually displayed in mathematical discourse, the mathematical fictionalist introduces a fictional operator: ‘According to mathematical theory M…’. Such an operator, however, changes the semantics of mathematical discourse. Applied to a true mathematical statement, at least one that the platonist recognizes as true, the result will be a true statement—even according to the mathematical fictionalist. For instance, from both platonist and fictionalist perspectives, the statement ‘according to arithmetic, there are infinitely many prime numbers’ comes out true. But, in this case, the mathematical fictionalist can no longer offer a unified semantics for mathematical and scientific languages, given that the latter does not involve the introduction of fictional operators. Thus, whether mathematical fictionalists are able to provide a uniform semantics ultimately depends on whether fictional operators are introduced or not.