Legal qualification of bitcoin, cryptocurrencies and "private money" in general raises doubts. Although, economically speaking, these goods perform some of the functions of money, they are not considered as such under the Polish civil code. This led some authors to argue that the rules on performance (and breach) of monetary obligations would not be applicable to cryptocurrencies. However, such a conclusion could cause unacceptable results, e.g. allowing for circumvention of the mandatory rules on maximum interest for late payment. The author proposes a solution to this dilemma. Firstly, it is accepted that cryptocurrencies are not "money" in the meaning of the Polish Civil Code. Therefore, the rules governing performance of monetary obligations do not automatically apply to cryptocurrencies. Secondly, cryptocurrencies cannot also be subject to all rules governing non-monetary performance, as this would lead to results inconsistent with the legislative purpose underlying various provisions of law. To ensure effectiveness of such provisions, a hybrid approach should be adopted. In particular, where justified by its ratio legis, the respective provisions governing monetary obligations should be applied to cryptocurrencies mutatis mutandi.