  In this paper, we generalize a result of Satoh to show that for any odd
natural $n$, the connected sum of the $n$-twist spun sphere of a knot $K$ and
an unknotted projective plane in the 4-sphere is equivalent to the same
unknotted projective plane. We additionally provide a fix to a small error in
Satoh's proof of the case that $K$ is a 2-bridge knot.
