diff --git a/algebra/frac.v b/algebra/frac.v
index 11cb32deab537850a9a6977cd4e385dab7f04ccd..bc9f469df7e6915c242b84c11e94597f155401bc 100644
--- a/algebra/frac.v
+++ b/algebra/frac.v
@@ -35,3 +35,6 @@ Global Instance frac_full_exclusive : Exclusive 1%Qp.
 Proof.
   move=> y /Qcle_not_lt [] /=. by rewrite -{1}(Qcplus_0_r 1) -Qcplus_lt_mono_l.
 Qed.
+
+Lemma frac_op': ∀ (p q: Qp), (p ⋅ q) = (p + q)%Qp.
+Proof. done. Qed.