Unrecognizability by spectrum of finite simple orthogonal groups of dimension nine

The spectrum of a finite group is the set of its elements orders. A group $G$ is said to be unrecognizable by spectrum if there are infinitely many pairwise non-isomorphic finite groups having the same spectrum as $G$. We prove that the simple orthogonal group $O_9(q)$ has the same spectrum as $V\rtimes O_8^-(q)$ where $V$ is the natural 8-dimensional module of the simple orthogonal group $O_8^-(q)$, and in particular $O_9(q)$ is unrecognizable by spectrum. Note that for $q=2$, the result was proved earlier by Mazurov and Moghaddamfar.