diff --git a/src/gpt_langchain.py b/src/gpt_langchain.py
index c082dcc74..d733e7491 100644
--- a/src/gpt_langchain.py
+++ b/src/gpt_langchain.py
@@ -2870,7 +2870,7 @@ def _get_request_payload(
                 "type": "text",
                 "text": system,
                 "cache_control": {"type": "ephemeral"}
-            }] if system else None
+            }] if system else ''
 
             # Process user and assistant messages
             messages_cached = self.process_messages(messages)
diff --git a/src/version.py b/src/version.py
index e023d9369..d8582d097 100644
--- a/src/version.py
+++ b/src/version.py
@@ -1 +1 @@
-__version__ = "16a758f7196ba5d094436c7c508a9694663fcfd5"
+__version__ = "2f283d091366111f2e004effefbe966b4b1fa006"