  We consider the possibility that the reactor antineutrino anomaly is due to a
miscalculation of one or more of the $^{235}\text{U}$, $^{238}\text{U}$,
$^{239}\text{Pu}$, and $^{241}\text{Pu}$ reactor antineutrino fluxes. From the
fit of the data we obtain the precise determination $\sigma_{f,235} = ( 6.33
\pm 0.08 ) \times 10^{-43} \, \text{cm}^2 / \text{fission}$ of the
$^{235}\text{U}$ cross section per fission, which is more precise than the
calculated value and differs from it by $2.2\sigma$. The cross sections per
fission of the other fluxes have large uncertainties and in practice their
values are undetermined by the fit. We conclude that it is very likely that at
least the calculation of the $^{235}\text{U}$ flux must be revised.
