It is expected that conformal symmetry is an emergent property of many systems at their critical point. This imposes strong constraints on the critical behavior of a given system. Taking them into account in theoretical approaches can lead to a better understanding of the critical physics or improve approximation schemes. However, within the framework of the non-perturbative or functional renormalization group and, in particular, of one of its most used approximation schemes, the Derivative Expansion (DE), non-trivial constraints only apply from third order (usually denoted O(@4)), at least in the usual formulation of the DE that includes correlation functions involving only the order parameter. In this work, we implement conformal constraints on a generalized DE including composite operators and show that new constraints already appear at second order of the DE (or O(@2)). We show how these constraints can be used to fix nonphysical regulator parameters.