  The exact way of treating flux shape uncertainties in unfolded, flux-averaged
neutrino cross-section measurements can lead to subtle issues when comparing
the results to model predictions. There is a difference between reporting a
cross section in the (unknown) real flux, and reporting a cross section that
was extrapolated from the (unknown) real flux to a fixed reference flux. A lot
of (most?) current analyses do the former, while the results are compared to
model predictions as if they were the latter. This leads to (part of) the flux
shape uncertainty being ignored, potentially leading to wrong physics
conclusions. The size of the effect is estimated to be sub-dominant, but
non-negligible in two example measurements from T2K and MINERvA. This paper
describes how the issue arises and provides instructions for possible ways how
to treat the flux shape uncertainties correctly.
