Magnetoresistivity and Hall resistivity of a bulk Bi₂Se₃ single crystal are investigated. It is found that in high magnetic fields (above 7 T), the Shubnikov – de Haas effect is observed. The Berry phase determined using the standard  Lifshitz – Onsager formalism is Ф_B ≈ 0.8π, which indicates the presence of Dirac fermions in the system. At the same time, Ф_B deviates from the ideal π value. It is shown that it is important to take into account the Zeeman interaction and the non-ideality of the Dirac dispersion relation for surface states for correct description of topological effects.