Traditional "activation" views of masked priming explain the identity priming effect in terms of facilitation due to 'pre-activation' of stored representations. Norris and Kinoshita's (2008) Bayesian Reader theory of masked priming instead explains priming in terms of the evidence that the prime contributes towards the decision required to the target. In support of the Bayesian Reader account, Norris and Kinoshita showed that the absence of priming for nonwords in the lexical decision task and for targets requiring a Different decision in the same-different match task can be explained based on a single principle. Against this, Bowers (2010) argued that the absence of priming should be explained instead by a combination of sublexical priming and "familiarity bias". As evidence, Bowers cited Bodner and Masson's (1997) finding that nonword priming did emerge with targets presented in visually unfamiliar cAsE-AlTeRnAtEd format. We present evidence that this finding was due to the use of an ambiguous letter in casealternated format; when using unambiguous letters, we consistently failed to find priming of case-alternated nonwords. We suggest that the Bayesian Reader, rather than the familiarity bias hypothesis, explains the absence of priming.