diff --git a/schema.json b/schema.json
index 15502e9b..ecd9b048 100644
--- a/schema.json
+++ b/schema.json
@@ -45,6 +45,10 @@
             "type": "string",
             "format": "uri"
         },
+        "$ref": {
+            "type": "string",
+            "format": "uriref"
+        },
         "title": {
             "type": "string"
         },