The aim of the article is to conduct a comparison, for the first time in historiography, of the ontology of socialism in the views of E. Guevara and N. Khessin. Both thinkers formulated the inherent contradiction that both the USSR and Cuba faced in their attempts to overcome the problems of capitalism and build a socialist society. We examine the history of political economy discussions in the 1960s in the USSR and in Cuba using the works of their participants. The comparative analysis leads to the conclusion that the theoretical position put forward by N. Khessin regarding the "economic cell," which posited that the fundamental production relation of socialism is the systematic planned organization of public production, resonated significantly with the perspective advocated by Ernesto Guevara during the economic debate in Cuba in the early 1960s. The Latin American revolutionary emphasized the central role of centralized planning in socialism. We show that political economy in the USSR and in Cuba continued to rely on the categories of commodity economy based on the separation of producers; however, the construction of socialism presupposed the abolition of this separation. Khessin and Guevara were able to articulate this objective contradiction at approximately the same time. The paper uncovers that Khessin's seminal article on the "economic cell" was published in a journal in Cuba edited by E. Guevara almost immediately after its release in the USSR.