diff --git a/importlib_metadata/__init__.py b/importlib_metadata/__init__.py
index e9af4972..9b912f8e 100644
--- a/importlib_metadata/__init__.py
+++ b/importlib_metadata/__init__.py
@@ -775,6 +775,7 @@ def children(self):
         return []
 
     def zip_children(self):
+        # deferred for performance (python/importlib_metadata#502)
         from zipp.compat.overlay import zipfile
 
         zip_path = zipfile.Path(self.root)