The Stern signatures are a class of lattice-based signatures constructed from Stern protocols, a special class of sigma protocols, admitting diverse functionalities with good asymptotic efficiency. However, the post-quantum security of existing Stern signatures is unclear, since they are built via the Fiat-Shamir transformation, which has not been proved to be secure in the quantum random oracle model (QROM). The goal of this paper is to find an alternative transformation for constructing post-quantum secure Stern signatures.