diff --git a/.github/workflows/nix.yml b/.github/workflows/nix.yml
index e24651aeb..3a4df1ac0 100644
--- a/.github/workflows/nix.yml
+++ b/.github/workflows/nix.yml
@@ -15,4 +15,4 @@ jobs:
           extra_nix_config: |
             extra-substituters = https://anmonteiro.nix-cache.workers.dev
             extra-trusted-public-keys = ocaml.nix-cache.com-1:/xI2h2+56rwFfKyyFVbkJSeGqSIYMC/Je+7XXqGKDIY=
-      - run: nix build -L .#cohttp-curl-lwt
+      - run: nix develop -c dune build @runtest @check
diff --git a/flake.nix b/flake.nix
index da89e0e1b..5b913c17c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -11,6 +11,7 @@
           inherit system;
           overlays = [
             (final: prev: {
+              openssl-oc = osuper.openssl_3_0;
               ocamlPackages = prev.ocamlPackages.overrideScope' (oself: osuper: {
                 ctypes-foreign = osuper.ctypes-foreign.overrideAttrs (_: { doCheck = false; });
                 ctypes = osuper.ctypes.overrideAttrs (_: { doCheck = false; });