All null for variable values.
diff --git a/src/main/resources/META-INF/feature/Feature-1.0.0.schema.json b/src/main/resources/META-INF/feature/Feature-1.0.0.schema.json
index 14d5c59..21067b6 100644
--- a/src/main/resources/META-INF/feature/Feature-1.0.0.schema.json
+++ b/src/main/resources/META-INF/feature/Feature-1.0.0.schema.json
@@ -32,7 +32,7 @@
       "type": "object",
       "patternProperties": {
         "^(.+)$": {
-          "type": "string"
+          "type": ["string","null"]
         }
       }
     },