This paper has two objectives. The first is to critically analyze the illusionist-realist debate about the existence of phenomenal consciousness. The second objective is to show that refuting illusionism is not as easy as most realists suppose. Many realists argue that illusionism is incoherent because it entails the falsity of a thesis that they take to be irrefutably true: when it comes to phenomenal properties, their appearance and their reality are indistinguishable. I label this thesis “No-Gap”. I explain that illusionists can oppose No-Gap, and accordingly conceive of introspection as capable of misrepresenting unproblematic “quasi-phenomenal properties” (Frankish 2016: 18) as authentic phenomenal properties. I then consider Anna Giustina’s introspective knowledge by acquaintance account, which can potentially disarm this illusionist argument against No-Gap. In her view, what she calls “primitive introspection” should provide a form of infallible knowledge of phenomenal appearances that can falsify the illusionist hypothesis. I claim that Giustina’s move fails to neutralize the illusionist hypothesis because the notion of infallible knowledge she proposes faces a knock-down dilemma: either it exploits a notion of infallibility that concedes that illusionism is a coherent possibility, or it relies on a notion of infallibility that jeopardizes primitive introspection as a source of infallible knowledge. Either way, the realist fails to support the existence of an infallible form of phenomenal knowledge that successfully rules out the illusionist hypothesis.