In Moksha Mordvin (Finno-Ugric), modifiers generally do not show concord with the noun but are inflected if the noun is elided. This paper argues that inflection under ellipsis has the same distribution as nominal concord and is best analyzed as such. Concord is a regular property of Moksha nominal syntax so that features are present on nominal modifiers in non-elliptical context as well but remain without morphological realization. Absence of overt concord exponents in non-elliptical contexts follows from the interaction between Spell-Out and Probe Conversion, an operation that applies to valued (or checked) probes and renders them eligible to the PF interface. More generally, this paper raises a question of interpretability at PF and proposes a hypothesis that all features triggering syntactic operations are uninterpretable at this interface.