diff --git a/aider/repomap.py b/aider/repomap.py
index 9b6342eae..e7d70df82 100644
--- a/aider/repomap.py
+++ b/aider/repomap.py
@@ -20,6 +20,9 @@ from .dump import dump  # noqa: F402
 
 
 def to_tree(tags):
+    if not tags:
+        return ""
+
     tags = sorted(tags)
 
     output = ""