  We present a search for flavor changing neutral currents in decays of top
quarks. The analysis is based on a search for ttbar -> l'null + jets (l, l' =
e, mu) final states using 4.1 fb^-1 of integrated luminosity of ppbar
collisions at sqrt(s) = 1.96 TeV. We extract limits on the branching ratio B(t
-> Zq) (q = u, c quarks), assuming anomalous tuZ or tcZ couplings. We do not
observe any sign of such anomalous coupling and set a limit of B < 3.2% at 95%
C.L.
