  Dong and Wang in [Theor. Comput. Sci. 771 (2019) 93--98] conjectured that the
resulting graph of the $n$-dimensional folded hypercube $FQ_n$ by deleting any
perfect matching is isomorphic to the hypercube $Q_n$. In this paper, we show
that the conjecture holds when $n=2,3$, and it is not true for $n\geq4$.
