Morphisms of presheaves from presheaf F to sheaf G

Question

There is the lemma that states that if f,g : F -> G are morphisms of sheaves, such that $\forall x \in X, f_x = g_x$, then f = g.

Is this true also if f,g : F -> G are morphisms of pre-sheaves, with G a sheaf (F pre-sheaf)?