Cognitive Radio (CR) technology constitutes a new paradigm where wireless devices can access the spectrum left unused by licensed or primary users in an opportunistic way. This feature opens the door to a main new threat: the Primary User Emulation (PUE) attack, in which a malicious user transmits a fake primary signal preventing a Cognitive Radio Network (CRN) from using the available spectrum. Cooperative location of a primary source can be a valuable tool for distinguishing between a legitimate transmission and a PUE attack whenever the position of primary users is known, as it is the case of TV towers in the IEEE 802.22 standard. However, the location process can be undermined due to false data provided by malicious or faulty nodes. In this paper, we analyze the effect of forged reports on the location process of a given emitter and provide a set of countermeasures in order to make it robust to undesired behaviors.