diff --git a/nixos/tests/common/acme/server/default.nix b/nixos/tests/common/acme/server/default.nix
index 1d6c2cc9d30a..36c1a477392c 100644
--- a/nixos/tests/common/acme/server/default.nix
+++ b/nixos/tests/common/acme/server/default.nix
@@ -76,6 +76,7 @@ let
     httpPort = 80;
     tlsPort = 443;
     ocspResponderURL = "http://0.0.0.0:4002";
+    strict = true;
   };
 
   pebbleConfFile = pkgs.writeText "pebble.conf" (builtins.toJSON pebbleConf);