  Both BaBar and Belle have found evidence for a non-zero width difference in
the $D^0$-$\bar D^0$ system. Although there is no direct experimental evidence
for CP-violation in $D$ mixing (yet), we show that the measured values of the
width difference $y\sim \Delta\Gamma$ already imply constraints on the
CP-violating phase in $D$ mixing, which, if significantly different from zero,
would be an unambiguous signal of new physics.
