  An $n \times n$ matrix $H$ is Butson-Hadamard if its entries are
$k^{\text{th}}$ roots of unity and it satisfies $HH^* = nI_n$. Write $BH(n, k)$
for the set of such matrices.
  Suppose that $k = p^{\alpha}q^{\beta}$ where $p$ and $q$ are primes and
$\alpha \geq 1$. A recent result of {\"O}sterg{\aa}rd and Paavola uses a matrix
$H \in BH(n,pk)$ to construct $H' \in BH(pn, k)$. We simplify the proof of this
result and remove the restriction on the number of prime divisors of $k$. More
precisely, we prove that if $k = mt$, and each prime divisor of $k$ divides
$t$, then we can construct a matrix $H' \in BH(mn, t)$ from any $H \in
BH(n,k)$.
