  We show that the existence of a coin-flipping protocol safe against
\emph{any} non-trivial constant bias (\eg $.499$) implies the existence of
one-way functions. This improves upon a recent result of Haitner and Omri [FOCS
'11], who proved this implication for protocols with bias $\frac{\sqrt2 -1}2 -
o(1) \approx .207$. Unlike the result of Haitner and Omri, our result also
holds for \emph{weak} coin-flipping protocols.
