  In 2003, it was claimed that the following problem was solvable in polynomial
time: do there exist k edge-disjoint paths of length exactly 3 between vertices
s and t in a given graph? The proof was flawed, and we show that this problem
is NP-hard even if we disallow multiple edges. We use a reduction from Partial
Orientation, a problem recently shown by P\'alv\"olgyi to be NP-hard.
