diff --git a/nixos/tests/cfssl.nix b/nixos/tests/cfssl.nix
index e291fc285fb..170f09d9b76 100644
--- a/nixos/tests/cfssl.nix
+++ b/nixos/tests/cfssl.nix
@@ -38,7 +38,7 @@ import ./make-test-python.nix ({ pkgs, ...} : {
   testScript =
   let
     cfsslrequest = with pkgs; writeScript "cfsslrequest" ''
-      curl -X POST -H "Content-Type: application/json" -d @${csr} \
+      curl -f -X POST -H "Content-Type: application/json" -d @${csr} \
         http://localhost:8888/api/v1/cfssl/newkey | ${cfssl}/bin/cfssljson /tmp/certificate
     '';
     csr = pkgs.writeText "csr.json" (builtins.toJSON {