Debate around inflectional morphology in language acquisition has contrasted various rule- versus analogy-based approaches. This paper tests the rule-based Tolerance Principle (TP) against a new type of pattern in the acquisition of the possessive suffix -im in Northern East Cree. When possessed, each noun type either requires or disallows the suffix, which has a complex distribution throughout the lexicon. Using naturalistic video data from one adult and two children -- Ani (2;01-4;03) and Daisy (3;08-5;10) -- this paper presents two studies. Study 1 applies the TP to the input to extrapolate two possible sets of nested rules for -im and make predictions for child speech. Study 2 tests these predictions and finds that each child's production of possessives over time is largely consistent with the predictions of the TP. This paper finds the TP can account for the acquisition of the possessive suffix and discusses implications for language science and Cree language communities.