diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index 9a3f662bc..317f83e66 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -1013,7 +1013,7 @@ def check_model_availability(io, client, main_model):
     except openai.NotFoundError:
         # Azure sometimes returns 404?
         # https://discord.com/channels/1131200896827654144/1182327371232186459
-        io.tool_error("Unable to list available models, proceeding with {main_model.name}")
+        io.tool_error(f"Unable to list available models, proceeding with {main_model.name}")
         return True
 
     model_ids = sorted(model.id for model in available_models)