diff --git a/skythought/evals/inference_and_check.py b/skythought/evals/inference_and_check.py
index 7a534565..f7210393 100644
--- a/skythought/evals/inference_and_check.py
+++ b/skythought/evals/inference_and_check.py
@@ -237,7 +237,7 @@ def generate_responses_for_dataset(
     # Prepare conversations
     conversations = handler.make_conversations(
         remaining_data,
-        str(model_config.system_prompt),
+        str(model_config.system_prompt) if model_config.system_prompt else None,
         model_config.user_template,
         model_config.assistant_prefill,
     )