diff --git a/opam b/opam
index e1d398034589669ff4a0a0239f7721edefc4a9cb..6fc80d868edbac37fe3d62ef0c274b2952f988df 100644
--- a/opam
+++ b/opam
@@ -9,6 +9,6 @@ build: [make "-j%{jobs}%"]
 install: [make "install"]
 remove: ["rm" "-rf" "%{lib}%/coq/user-contrib/reloc"]
 depends: [
-  "coq-iris-heap-lang" { (= "dev.2021-09-06.2.95df9887") | (= "dev") }
+  "coq-iris-heap-lang" { (= "dev.2021-12-09.1.f52f9f6a") | (= "dev") }
   "coq-autosubst" { = "dev" }
 ]
diff --git a/theories/typing/types.v b/theories/typing/types.v
index 664498d0319a1b900e01271cbc18974dd3f6b8e4..17a8508e9b83976fcc5bd6e3a2122d16f2039029 100644
--- a/theories/typing/types.v
+++ b/theories/typing/types.v
@@ -296,7 +296,7 @@ Proof.
     | [ H : ∀ xs ys, xs ≡ₚ ys → is_closed_expr xs _ = is_closed_expr ys _
       |- is_closed_expr _ _ = is_closed_expr _ _ ] => eapply H; eauto
     end; try done.
-  - apply bool_decide_iff. by rewrite Hxsys.
+  - apply bool_decide_ext. by rewrite Hxsys.
   - by rewrite Hxsys.
 Qed.