diff --git a/prelude/co_pset.v b/prelude/co_pset.v
index 55efb4f7851d7383c3e01b9d07969041ed42bfa1..7516f56cda8f9971b0d052a15e15bf267ff20c56 100644
--- a/prelude/co_pset.v
+++ b/prelude/co_pset.v
@@ -332,6 +332,12 @@ Proof.
   * by intros [q' ->]; induction q; simpl; rewrite ?coPset_elem_of_node.
 Qed.
 
+Lemma coPset_suffixes_infinite p : ¬set_finite (coPset_suffixes p).
+Proof.
+  rewrite coPset_finite_spec; simpl.
+  (* FIXME no time to finish right now, but I think it holds *)
+Abort. 
+
 (** * Splitting of infinite sets *)
 Fixpoint coPset_l_raw (t : coPset_raw) : coPset_raw :=
   match t with