The traditional Lockean justification of property rights has been argued to be no longer valid in a world in which much wealth does not derive from acquisitions of natural resources, and in which much property, such as money, is intangible. This means that libertarians need to reconsider whether and why property rights are justified for objects that fall outside of the scope of the Lockean justification. This paper gives a justification of property rights in relation to modern money, which uses the self-ownership principle as its central premise. Since modern money is a form of credit, I start with a justification of credit property rights. I then consider both money under gold convertibility and present-day fiat systems, showing that the justification of credit property rights remains valid under these conditions.