diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 6bc56d6..67a3c37 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -28,7 +28,14 @@ jobs:
       - name: Flake checks 🧪
         run: |
           # Because 'nix flake check' is not system-aware
-          # See https://srid.ca/haskell-template/checks
-          nix run nixpkgs#sd 'systems = nixpkgs.lib.systems.flakeExposed' 'systems = [ "x86_64-linux" ]' flake.nix
+          # See https://srid.ca/haskell-flake/checks
+          nix run nixpkgs#sd \
+            'systems = nixpkgs.lib.systems.flakeExposed' \
+            'systems = [ "x86_64-linux" ]' \
+            flake.nix
 
-          nix flake check -L
+          # Sandbox must be disabed for:
+          # https://github.com/srid/haskell-flake/issues/21
+          nix \
+            --option sandbox false \
+            flake check -L
diff --git a/flake.nix b/flake.nix
index 59c4de6..6513ba6 100644
--- a/flake.nix
+++ b/flake.nix
@@ -49,7 +49,7 @@
             tools = hp: {
               treefmt = config.treefmt.build.wrapper;
             } // config.treefmt.build.programs;
-            hlsCheck.enable = false;
+            hlsCheck.enable = true;
             hlintCheck.enable = true;
           };
         };