diff --git a/anki/history.py b/anki/history.py
index 44230599b..60a52b3a1 100644
--- a/anki/history.py
+++ b/anki/history.py
@@ -5,7 +5,12 @@
 """\
 History - keeping a record of all reviews
 ==========================================
+
+If users run 'check db', duplicate records will be inserted into the DB - I
+really should have used the time stamp as the key. You can remove them by
+keeping the lowest id for any given timestamp.
 """
+
 __docformat__ = 'restructuredtext'
 
 import time