diff --git a/aider/args_formatter.py b/aider/args_formatter.py
index 7e58c604e..c7672ccba 100644
--- a/aider/args_formatter.py
+++ b/aider/args_formatter.py
@@ -143,7 +143,10 @@ class YamlHelpFormatter(argparse.HelpFormatter):
             default = "true"
 
         if default:
-            parts.append(f"#{switch}: {default}\n")
+            if "#" in default:
+                parts.append(f'#{switch}: "{default}"\n')
+            else:
+                parts.append(f"#{switch}: {default}\n")
         elif action.nargs in ("*", "+") or isinstance(action, argparse._AppendAction):
             parts.append(f"#{switch}: xxx")
             parts.append("## Specify multiple values like this:")