diff --git a/kanbanize_sdk/endpoints/users.py b/kanbanize_sdk/endpoints/users.py
index 3f209a8..daf8908 100644
--- a/kanbanize_sdk/endpoints/users.py
+++ b/kanbanize_sdk/endpoints/users.py
@@ -39,7 +39,7 @@ def insert(self, body: UsersInsertBody | dict) -> dict:
 
         payload = body.to_dict() if isinstance(body, UsersInsertBody) else body
 
-        return self.service.post(self.endpoint + '/invite', json=payload)
+        return self.service.post(self.endpoint + '/invite', data=payload)
 
     def get(self, user_id: int) -> dict:
         """