diff --git a/aider/coders/senior_coder.py b/aider/coders/senior_coder.py
index aac4867a7..84669983c 100644
--- a/aider/coders/senior_coder.py
+++ b/aider/coders/senior_coder.py
@@ -16,8 +16,12 @@ class SeniorCoder(AskCoder):
             return
 
         kwargs = dict()
-        kwargs["main_model"] = Model(self.main_model.junior_model_name)
-        kwargs["edit_format"] = self.main_model.junior_edit_format
+        
+        # Use the junior_model from the main_model if it exists, otherwise use the main_model itself
+        junior_model = self.main_model.junior_model or self.main_model
+        
+        kwargs["main_model"] = junior_model
+        kwargs["edit_format"] = junior_model.edit_format
         kwargs["suggest_shell_commands"] = False
         kwargs["map_tokens"] = 0
         kwargs["total_cost"] = self.total_cost