diff --git a/src/calibre/db/__init__.py b/src/calibre/db/__init__.py
index 930b99f8bf..a989e45dce 100644
--- a/src/calibre/db/__init__.py
+++ b/src/calibre/db/__init__.py
@@ -139,4 +139,5 @@ Various things that require other things before they can be migrated:
     3. Check that content server reloading on metadata,db change, metadata
     backup, refresh gui on calibredb add and moving libraries all work (check
     them on windows as well for file locking issues)
+    4. Check for mem leaks when switching libraries
 '''