As a step towards writing down associativity conditions for a general extended conformal algebra, we consider Jacobi's identity for a set of quasi-primary fields. In particular, we show that the identity for the subalgebra of operators which generate symmetries of the vacuum can be written in terms of Racah coefficients for su(2). The associativity condition for the full algebra is obtained in an explicit form by considering crossing symmetry of the four-point functions.