diff --git a/aider/models.py b/aider/models.py
index 09c250da5..b9ae02590 100644
--- a/aider/models.py
+++ b/aider/models.py
@@ -328,7 +328,10 @@ class Model:
         self.missing_keys = res.get("missing_keys")
         self.keys_in_environment = res.get("keys_in_environment")
 
-        if self.info.get("max_input_tokens", 0) < 32 * 1024:
+        max_input_tokens = self.info.get("max_input_tokens")
+        if not max_input_tokens:
+            max_input_tokens = 0
+        if max_input_tokens < 32 * 1024:
             self.max_chat_history_tokens = 1024
         else:
             self.max_chat_history_tokens = 2 * 1024