diff --git a/lib/jsonschema/default.nix b/lib/jsonschema/default.nix
index df3f63b8..0a92da9b 100644
--- a/lib/jsonschema/default.nix
+++ b/lib/jsonschema/default.nix
@@ -47,7 +47,7 @@ rec {
     let
       evaled = lib.evalModules { modules = [ module ]; };
     in
-    parseOptions evaled.options;
+    { "$schema" = "http://json-schema.org/draft-07/schema#"; } // parseOptions evaled.options;
 
   # parses a set of evaluated nixos options to a jsonschema
   parseOptions =
@@ -66,6 +66,7 @@ rec {
     // {
       type = "object";
       inherit properties;
+      additionalProperties = false;
     };
 
   # parses and evaluated nixos option to a jsonschema property definition
diff --git a/lib/jsonschema/example-schema.json b/lib/jsonschema/example-schema.json
index 0073369e..1538a680 100644
--- a/lib/jsonschema/example-schema.json
+++ b/lib/jsonschema/example-schema.json
@@ -59,9 +59,8 @@
             "type": "string"
           }
         },
-        "required": [
-          "repo"
-        ],
+        "required": ["repo"],
+        "additionalProperties": false,
         "type": "object"
       },
       "default": {},