  The treatment of $\gamma_{5}$ in Dimensional Regularization leads to
ambiguities in field-theoretic calculations, of which one example is the
coefficient of a particular term in the four-loop gauge $\beta$-functions of
the Standard Model. Using Weyl Consistency Conditions, we present a
scheme-independent relation between the coefficient of this term and a
corresponding term in the three-loop Yukawa $\beta$-functions, where a
semi-na\"ive treatment of $\gamma_{5}$ is sufficient, thereby fixing this
ambiguity. We briefly outline an argument by which the same method fixes
similar ambiguities at higher orders.
