diff --git a/tiramisu_json_api/api.py b/tiramisu_json_api/api.py
index 8026194..67df2dd 100644
--- a/tiramisu_json_api/api.py
+++ b/tiramisu_json_api/api.py
@@ -627,7 +627,6 @@ class Config:
     def is_hidden(self,
                    path: str,
                    index: Optional[int]) -> bool:
-        property_ = 'hidden'
         for property_, needs in {'hidden': True, 'display': False}.items():
             if property_ in self.temp.get(path, {}):
                 value = self.temp[path][property_]
@@ -638,7 +637,7 @@ class Config:
                 elif self.model.get(path, {}).get(property_, None) == needs:
                     return True
                 index = str(index)
-                if index is not None and index in self.model.get(path, {}) and self.model.get(path, {}).get(index, {}).get(property_, None) == needs:
+                if index != 'None' and index in self.model.get(path, {}) and self.model.get(path, {}).get(index, {}).get(property_, None) == needs:
                     return True
         return False