  We calculate the subleading twist contributions to the endpoint of the
inclusive lepton energy spectrum in B -> X_u l \nu. We show that the same two
subleading twist functions that appear in the decay B -> X_s \gamma govern the
subleading effects in this decay. Using these results we find large
O(Lambda/mB) corrections to the determination of |Vub| from the endpoint of the
charged lepton spectrum. Using a simple model for the relevant subleading shape
functions, we estimate the uncertainty in |Vub| from Lambda/mb corrections to
be at the ~ 15% level for a lower lepton energy cut of 2.2 GeV.
