We used event-related potentials to investigate how markedness impacts person agreement in English-speaking learners of L2-Spanish. Markedness was examined by probing agreement with both first-person (marked) and third-person (unmarked) subjects. Agreement was manipulated by crossing first-person subjects with third-person verbs and vice versa. Native speakers showed a P600 for both errors, larger for first-person subject + third-person verb violations. This aligns with claims that, when the first element in the dependency is marked (first person), the parser generates stronger predictions regarding upcoming agreeing elements using feature activation. Twenty-two upper-intermediate/advanced learners elicited a P600 across both errors. Learners were equally accurate detecting both errors, but the P600 was marginally reduced for first-person subject + third-person verb violations, suggesting that learners overused unmarked forms (third person) online. However, this asymmetry mainly characterized lower-proficiency learners. Results suggest that markedness impacts L2 agreement without constraining it, although learners are less likely to use marked features top-down.