diff --git a/tiramisu_json_api/api.py b/tiramisu_json_api/api.py
index 595846a..8d8e13a 100644
--- a/tiramisu_json_api/api.py
+++ b/tiramisu_json_api/api.py
@@ -420,6 +420,7 @@ class ContextOption(_Option):
         self.form = form
         self.schema = {'properties': schema}
         self.temp = temp
+        self.index = None 
 
     def __call__(self,
                  path: str,