  We expose a potential flaw in standard treatments of weak decay amplitudes,
including that of epsilon'/epsilon. We show that (contrary to conventional
wisdom) dimension-eight operators do contribute to weak amplitudes, at order
G_F alpha_s and without 1/M_W^2 suppression. We demonstrate the existence of
these operators with a simple weak hamiltonian and proceed to discuss their
contribution in a general context. We estimate the effect of dimension-eight
operators to be at the 100% level in a sum rule determination of the operator
O_7 for mu = 1.5 GeV, suggesting presently available values of mu are too low
to justify neglect of these effects.
