In our earlier work [Shahbazapnahi, S et al., (2004)], we have developed a new approach to estimate the channel matrix in orthogonal space-time block code (OSTBC) based communication systems. This approach can be used to decode most OSTBCs in a completely blind fashion. However, there are a few OSTBCs for which the aforementioned technique does not work because of the channel nonidentifiability. We first study the channel estimation ambiguity for the OSTBCs which is caused by such a nonidentifiability. We then propose a simple linear precoding technique which resolves this ambiguity.