diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f949c4ee..721cfdd2 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -5,21 +5,39 @@ on:
    branches:
      - master
 jobs:
-  tests:
-    runs-on: ubuntu-latest
+  macOS:
+    runs-on: macos-latest
     strategy:
+      fail-fast: false
       matrix:
-        ocamlVersion: [4_08, 4_10, 4_11, 4_12]
+        # Tests only on 2 latest versions as macOS runners are more expensive
+        ocamlVersion: [4_11, 4_12]
     steps:
     - uses: actions/checkout@v2
       with:
         submodules: 'recursive'
     - uses: cachix/install-nix-action@v12
-      with:
-        skip_adding_nixpkgs_channel: true
     - uses: cachix/cachix-action@v8
       with:
         name: anmonteiro
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
+    - name: "Run nix-build"
+      run: nix-build ./nix/ci/test.nix -A native --argstr ocamlVersion ${{ matrix.ocamlVersion }}
+
+  linux:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        ocamlVersion: [4_08, 4_10, 4_11, 4_12]
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        submodules: 'recursive'
+    - uses: cachix/install-nix-action@v13
+    - uses: cachix/cachix-action@v10
+      with:
+        name: anmonteiro
+        signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
     - name: "Run nix-build"
       run: nix-build ./nix/ci/test.nix -A native -A musl64 --argstr ocamlVersion ${{ matrix.ocamlVersion }}
diff --git a/nix/ci/test.nix b/nix/ci/test.nix
index 0cac32a5..b2fe70a4 100644
--- a/nix/ci/test.nix
+++ b/nix/ci/test.nix
@@ -26,7 +26,6 @@ let
       buildInputs = (lib.attrValues piafDrvs) ++ (with ocamlPackages; [ ocaml dune findlib pkgs.ocamlformat ]);
       doCheck = true;
       checkPhase = ''
-        echo OI
         # Check code is formatted with OCamlformat
         dune build @fmt
       '';
diff --git a/nix/sources.nix b/nix/sources.nix
index 7b03906e..84673115 100644
--- a/nix/sources.nix
+++ b/nix/sources.nix
@@ -2,7 +2,7 @@
 let
   overlays =
     builtins.fetchTarball
-      https://github.com/anmonteiro/nix-overlays/archive/68b87e980.tar.gz;
+      https://github.com/anmonteiro/nix-overlays/archive/58960d0.tar.gz;
 
 in
 import "${overlays}/sources.nix" {
diff --git a/vendor/ocaml-h2 b/vendor/ocaml-h2
index a696a1ce..93c7e071 160000
--- a/vendor/ocaml-h2
+++ b/vendor/ocaml-h2
@@ -1 +1 @@
-Subproject commit a696a1ce66f573c23041840322d0e1770d5ebc70
+Subproject commit 93c7e071a0bf8e0b7360cc9d7dc4532cbe0943e9