diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index d97c1eafd..d738e4f2c 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -89,6 +89,7 @@ class Coder:
     message_tokens_sent = 0
     message_tokens_received = 0
     add_cache_headers = False
+    cache_warming_thread = None
 
     @classmethod
     def create(