diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 6ff7fe08d13..0e30f580ec8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -35,7 +35,11 @@ jobs:
     - run: nix-env -iA nix-build-uncached -f nix/
 
     - name: "nix-build"
-      run: nix-build-uncached --max-jobs 4 -A all-systems-go -build-flags -L
+      run: |
+        nix-instantiate -A ic-ref-run
+        nix show-derivation /nix/store/v37v69dy1l9krqwwnkm06argiqs3ajps-ic-ref-run.drv
+        nix-store --realise --substituters https://ic-hs-test.cachix.org /nix/store/r1qhqrav1h74c296hdbfyl21qjjbipnm-ic-ref-run || true
+        nix-build --max-jobs 4 -A all-systems-go
 
     - name: Calculate performance delta
       if: github.actor != 'dependabot[bot]' && runner.os == 'Linux' && github.event_name == 'pull_request'
diff --git a/nix/sources.json b/nix/sources.json
index c2983d8319e..0607476134b 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -103,10 +103,10 @@
         "homepage": null,
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "f696f72a73467defc6996a72546626f1872716a9",
-        "sha256": "1cawvpq3jh3lns3lhpbc5k43v8ajqii337z21n32yrhkcjjry7k8",
+        "rev": "eaf03591711b46d21abc7082a8ebee4681f9dbeb",
+        "sha256": "1shmhx8562gf2fnm74gyax1x24xdi8mlzhqnzgmglsd1c7jijgi1",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/f696f72a73467defc6996a72546626f1872716a9.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/eaf03591711b46d21abc7082a8ebee4681f9dbeb.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs-mozilla": {