diff --git a/prelude/tactics.v b/prelude/tactics.v
index fabd259de524e37c005cc2359f962ec8f334ff8a..98c88fe99693d909012237e02ba50dff5ae36f21 100644
--- a/prelude/tactics.v
+++ b/prelude/tactics.v
@@ -250,11 +250,13 @@ Ltac setoid_subst :=
| H : @equiv ?A ?e _ ?x |- _ => symmetry in H; setoid_subst_aux (@equiv A e) x
end.
-(** f_equiv works on goals of the form "f _ = f _", for any relation and any
-number of arguments. It looks for an appropriate "Proper" instance, and applies
+(** f_equiv works on goals of the form [f _ = f _], for any relation and any
+number of arguments. It looks for an appropriate [Proper] instance, and applies
it. The tactic is somewhat limited, since it cannot be used to backtrack on
the Proper instances that has been found. To that end, we try to ensure the
-trivial instance in which the resulting goals have an [eq]. *)
+trivial instance in which the resulting goals have an [eq]. More generally,
+when having [Proper (equiv ==> dist) f] and [Proper (dist ==> dist) f], it will
+favor the second. *)
Ltac f_equiv :=
match goal with
| _ => reflexivity