  We study causality violation in holographic hydrodynamics in the gauge
theory/string theory correspondence, focussing on Gauss-Bonnet gravity. The
value of the Gauss-Bonnet coupling is related to the difference between the
central charges of the dual conformal gauge theory. We show that, when this
difference is sufficiently large, causality is violated both in the
second-order truncated theory of hydrodynamics, as well as in the exact theory.
We find that the latter provides more stringent constraints, which match
precisely those appearing in the CFT analysis of Hofman and Maldacena.
