diff --git a/theories/hashset.v b/theories/hashset.v
index 920b49495980f659175e55efad3dcbbe8a336579..1ed944a9f287a1447de22b64d05d1c78f82689ed 100644
--- a/theories/hashset.v
+++ b/theories/hashset.v
@@ -104,6 +104,7 @@ Proof.
     intros (l&?&?). exists (hash x, l); simpl. by rewrite elem_of_map_to_list.
   - unfold elements, hashset_elements. intros [m Hm]; simpl.
     rewrite map_Forall_to_list in Hm. generalize (NoDup_fst_map_to_list m).
+    (* FIXME: trailing [?] works around Coq bug #12944. *)
     induction Hm as [|[n l] m' [??] Hm ?];
       csimpl; inversion_clear 1 as [|?? Hn]; [constructor|].
     apply NoDup_app; split_and?; eauto.
diff --git a/theories/sorting.v b/theories/sorting.v
index afdab4957007a1561530605f8bc329581bf2ec7a..d405d4c0df1ba6fd6079c3ab974aedf9e0c883b7 100644
--- a/theories/sorting.v
+++ b/theories/sorting.v
@@ -180,6 +180,7 @@ Section merge_sort_correct.
     Sorted R l1 → Sorted R l2 → Sorted R (list_merge R l1 l2).
   Proof.
     intros Hl1. revert l2. induction Hl1 as [|x1 l1 IH1];
+      (* FIXME: trailing [?] works around Coq bug #12944. *)
       induction 1 as [|x2 l2 IH2 ?]; rewrite ?list_merge_cons; simpl;
       repeat case_decide;
       repeat match goal with H : ¬R _ _ |- _ => apply total_not in H end;