The aim of this paper is to examine some formulations of fallibilism about knowledge and show that the precise formulation of fallibilism that can safely be regarded as true or plausible is not easily available. We start by discussing Jason Stanley's formulation of fallibilism and will sketch some difficulties that it will face. Although we mainly focus on his version of fallibilism, the same points can equally apply to variants of it. We will then examine Stanley's fallibilism in relation to his interest-relative invariantism, and reveal the difficulties Stanley's fallibilism faces in accommodating the interest-relativity. In fact, fallibilism should be an unnecessary additional concession to skepticism for interest-relative invariantists in general, and we argue that they even have a good reason to be infallibilists.