Let $U = \mathbf U(q)$ be a Sylow $p$-subgroup of a finite Chevalley group $G
= \mathbf G(q)$. In [GR}] R\"ohrle and the second author determined a
parameterization of the conjugacy classes of $U$, for $\mathbf G$ of small rank
when $q$ is a power of a good prime for $\mathbf G$. As a consequence they
verified that the number $k(U)$ of conjugacy classes of $U$ is given by a
polynomial in $q$ with integer coefficients. In the present paper, we consider
the case when $p$ is a bad prime for $\mathbf G$.