The functioning of language as a communication system is described by a variety of linguistic theories which are not always consistent with each other and often do not rely on cognitive and/or neurobiological data. One of the most striking examples is the “null morpheme” proposed by the theory of universal grammar, which is a concept that has only an abstract meaning as it has no phonological implementation (for example, the null ending of nouns in some cases: cf. stol-∅ (table_NOM) vs. stol-a (table_GEN). With the aim of testing the processing of null morphemes by the brain, we conducted an EEG experiment in which subjects were presented with heard phrases with null (e.g., on kupil-∅) (he bought-∅) or marked (ona kupil-a) (she bought_FEM) verb endings, with correct and incorrect gender agreement between the pronoun and the verb (e.g., on kupil-∅ (he bought-∅) vs. *ona kupil-∅ (she bought-∅, where the correct ending is –a)) and the verb presented alone (kupil-∅) (bought-∅) as a control condition. Event-related potentials analysis results demonstrated an increase in cerebral responses where the null ending disagreed. The latency of this response was ~200 msec, corresponding to the ELAN component, which reflects the early automatic processing of (morpho)syntactic information. These results can be explained by the theory of morphosyntactic priming and indicate that a representation of the null morpheme (ending) exists and is activated in the process of speech perception.