Along with progressive socio-economic development, relevant legal regulations should undergo appropriate changes. A significant value of a legal system constructed in such a manner should be a certain minimum level of multidimensional consistency, both within a specific branch of regulation and across all branches of law that constitute the legal system. However, an analysis of current legislation clearly indicates that inheritance law – despite the pursuit of a uniform legal system – is an area where numerous incoherencies can be observed. These occur in the scope of interpretation and practice, competing values underlying the drafted provisions, and the objectives set for individual regulations. The aim of this paper is to identify examples supporting the thesis that the principle of the uniformity of the legal system is not always fully and consistently implemented by the legislator. The indicated discrepancies often lead to significant dysfunctions of legal provisions, which destabilize the system of protecting the rights of heirs and the legal relations shaped after the testator’s decease.