We show that the classical Shinbrot's criteria to guarantee that a Leray-Hopf solution satisfies the energy equality follows trivially from the L 4 ((0 , T ) × Ω)) Lions-Prodi particular case. Moreover we extend Shinbrot's result to space coefficients r ∈ (3, 4) . In this last case our condition coincides with Shinbrot condition for r = 4, but for r < 4 it is more restrictive than the classical one, 2/p + 2/r = 1 . It looks significant that in correspondence to the extreme values r = 3 and r = ∞, and just for these two values, the conditions become respectively u ∈ L ∞ (L 3 ) and u ∈ L 2 (L ∞ ), which imply regularity by appealing to classical Ladyzhenskaya-Prodi-Serrin (L-P-S) type conditions. However, for values r ∈ (3, ∞) the L-P-S condition does not apply, even for the more demanding case 3 < r < 4 . The proofs are quite trivial, by appealing to interpolation, with L ∞ (L 2 ) in the first case and with L 2 (L 6 ) in the second case. The central position of this old classical problem in Fluid-Mechanics, together with the simplicity of the proofs (in particular the novelty of the second result) looks at least curious. This may be considered a merit of this very short note.Mathematics Subject Classification: 35Q30, 76A05, 76D03.