diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index 2f04026140..cc8cde8304 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -1230,7 +1230,7 @@ class Cache(object):
         if mi contains empty values. In this case, 'None' is distinguished from
         'empty'. If mi.XXX is None, the XXX is not replaced, otherwise it is.
         The tags, identifiers, and cover attributes are special cases. Tags and
-        identifiers cannot be set to None so then will always be replaced if
+        identifiers cannot be set to None so they will always be replaced if
         force_changes is true. You must ensure that mi contains the values you
         want the book to have. Covers are always changed if a new cover is
         provided, but are never deleted. Also note that force_changes has no