diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 4fee81d28c272ec8ea52ee9bbda7b74beafedb0b..d66b122bef82338aaa58bf9948a55bd5f2c9cda1 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -48,10 +48,10 @@ build-coq.dev:
     OCAML: "ocaml-base-compiler.4.14.0" # for faster rebuilds
     OPAM_PINS: "coq version dev"
 
-build-coq.8.19.0:
+build-coq.8.20.0:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.19.0"
+    OPAM_PINS: "coq version 8.20.0"
     DENY_WARNINGS: "1"
     MANGLE_NAMES: "1"
     # Coq bench needs an opam package
@@ -60,18 +60,18 @@ build-coq.8.19.0:
   - fp-timing
 
 # Separate MR job that does not run on fp-timing.
-build-coq.8.19.0-mr:
+build-coq.8.20.0-mr:
   <<: *template
   <<: *only_mr
   variables:
-    OPAM_PINS: "coq version 8.19.0"
+    OPAM_PINS: "coq version 8.20.0"
     MANGLE_NAMES: "1"
     DENY_WARNINGS: "1"
 
 trigger-iris.timing:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.19.0   git+https://gitlab.mpi-sws.org/$IRIS_REPO#$IRIS_REV"
+    OPAM_PINS: "coq version 8.20.0   git+https://gitlab.mpi-sws.org/$IRIS_REPO#$IRIS_REV"
   tags:
   - fp-timing
   only:
diff --git a/README.md b/README.md
index 64057581083d0b35a4df8907e738dbf12bcab5a6..47c0292ce171eb0bc2e91842c6870712219f195b 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ Some example verification demonstrating the use of Iris.
 
 This version is known to compile with:
 
- - Coq 8.19.0
+ - Coq 8.20.0
  - A development version of [Iris](https://gitlab.mpi-sws.org/iris/iris)
  - A development version of [Autosubst](https://github.com/coq-community/autosubst)
 
diff --git a/_CoqProject b/_CoqProject
index a5316e76dc2151fca37eb29249a85f8d349f00b3..7a631b7f83515cdfc6f494d2b0c3c756a7895b9b 100644
--- a/_CoqProject
+++ b/_CoqProject
@@ -4,6 +4,8 @@
 # Cannot use non-canonical projections as it causes massive unification failures
 # (https://github.com/coq/coq/issues/6294).
 -arg -w -arg -redundant-canonical-projection
+# Warning seems incorrect, see https://gitlab.mpi-sws.org/iris/stdpp/-/issues/216
+-arg -w -arg -notation-incompatible-prefix
 
 theories/barrier/proof.v
 theories/barrier/specification.v
diff --git a/theories/logrel/F_mu_ref_conc/typing.v b/theories/logrel/F_mu_ref_conc/typing.v
index 799148654296604b19465b766a57a44951d6ab50..1af4089e31e7208a484e5fcf67fdbd990a52731d 100644
--- a/theories/logrel/F_mu_ref_conc/typing.v
+++ b/theories/logrel/F_mu_ref_conc/typing.v
@@ -147,7 +147,7 @@ Proof.
     match goal with H : context[_ → _ ⊢ₜ _ : _] |- _ => rename H into IH end.
     specialize (IH
       (subst (ren (+1)) <$> Γ1) (subst (ren (+1)) <$> Γ2) (subst (ren (+1)) <$> ξ)).
-    rewrite ?map_length in IH.
+    rewrite ?length_map in IH.
     repeat rewrite fmap_app. apply IH.
     by repeat rewrite fmap_app.
   - econstructor; eauto.
@@ -155,7 +155,7 @@ Proof.
     match goal with H : context[_ → _ ⊢ₜ _ : TExist ?t] |- _ => rename t into τ end.
     specialize (IH
       (τ :: (subst (ren (+1)) <$> Γ1)) (subst (ren (+1)) <$> Γ2) (subst (ren (+1)) <$> ξ)).
-    asimpl in IH. rewrite ?map_length in IH.
+    asimpl in IH. rewrite ?length_map in IH.
     repeat rewrite fmap_app. apply IH.
     by repeat rewrite fmap_app.
 Qed.