diff --git a/tokencost/callbacks/llama_index.py b/tokencost/callbacks/llama_index.py
index ee4ef8e..d11c1ab 100644
--- a/tokencost/callbacks/llama_index.py
+++ b/tokencost/callbacks/llama_index.py
@@ -39,6 +39,8 @@ def _calc_llm_event_cost(self, payload: dict) -> None:
             estimates = calculate_all_costs_and_tokens(
                 messages_str, response, self.model
             )
+        else:
+            return
 
         self.prompt_cost += estimates["prompt_cost"]
         self.completion_cost += estimates["completion_cost"]