diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index ad75e8ebe..2c811ae84 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -547,11 +547,21 @@ class Coder:
             total_tokens = 0
 
         messages += self.cur_messages
-        messages[-1]["content"] += "\n\n" + self.fmt_system_prompt(self.gpt_prompts.system_reminder)
+
+        final = messages[-1]
 
         # Add the reminder prompt if we still have room to include it.
-        # if total_tokens < self.main_model.info.get("max_input_tokens", 0):
-        #    messages += reminder_message
+        if total_tokens < self.main_model.info.get("max_input_tokens", 0):
+            if self.main_model.accepts_multi_system_msgs:
+                messages += reminder_message
+            elif final["role"] == "user":
+                # stuff it into the user message
+                new_content = (
+                    final["content"]
+                    + "\n\n"
+                    + self.fmt_system_prompt(self.gpt_prompts.system_reminder)
+                )
+                messages[-1] = dict(role=final["role"], content=new_content)
 
         return messages
 
diff --git a/aider/models.py b/aider/models.py
index 6c0e8b057..68af6e5db 100644
--- a/aider/models.py
+++ b/aider/models.py
@@ -235,6 +235,9 @@ class Model:
             self.send_undo_reply = True
             return  # <--
 
+        if "gpt-3.5" in model or "gpt-4" in model:
+            self.accepts_multi_system_msgs = True
+
         # use the defaults
         if self.edit_format == "diff":
             self.use_repo_map = True