diff --git a/src/calibre/db/backend.py b/src/calibre/db/backend.py
index db5510d055..05a8887576 100644
--- a/src/calibre/db/backend.py
+++ b/src/calibre/db/backend.py
@@ -1485,7 +1485,7 @@ class DB(object):
         if not self.is_case_sensitive:
             for x in items:
                 path_map[x.lower()] = x
-            items = set(path_map)
+            items = {x.lower() for x in items}
             paths = {x.lower() for x in paths}
         items = items.intersection(paths)
         return items, path_map
diff --git a/src/calibre/db/tests/legacy.py b/src/calibre/db/tests/legacy.py
index c936367ba4..55610f6401 100644
--- a/src/calibre/db/tests/legacy.py
+++ b/src/calibre/db/tests/legacy.py
@@ -167,7 +167,6 @@ class LegacyTest(BaseTest):
 
         for meth, args in {
             'find_identical_books': [(Metadata('title one', ['author one']),), (Metadata('unknown'),), (Metadata('xxxx'),)],
-            'get_top_level_move_items': [()],
             'get_books_for_category': [('tags', newstag), ('#formats', 'FMT1')],
             'get_next_series_num_for': [('A Series One',)],
             'get_id_from_uuid':[('ddddd',), (db.uuid(1, True),)],
@@ -241,6 +240,10 @@ class LegacyTest(BaseTest):
             for a in args:
                 self.assertEqual(fmt(getattr(db, meth)(*a)), fmt(getattr(ndb, meth)(*a)),
                                  'The method: %s() returned different results for argument %s' % (meth, a))
+        def f(x, y):  # get_top_level_move_items is broken in the old db on case-insensitive file systems
+            x.discard('metadata_db_prefs_backup.json')
+            return x, y
+        self.assertEqual(f(*db.get_top_level_move_items()), f(*ndb.get_top_level_move_items()))
         d1, d2 = BytesIO(), BytesIO()
         db.copy_cover_to(1, d1, True)
         ndb.copy_cover_to(1, d2, True)