diff --git a/beets/importer.py b/beets/importer.py
index 344e382dd..a1248acbb 100644
--- a/beets/importer.py
+++ b/beets/importer.py
@@ -549,7 +549,7 @@ class ImportTask(object):
         self.replaced_items = defaultdict(list)
         for item in self.imported_items():
             dup_items = lib.items(dbcore.query.BytesQuery('path', item.path))
-            self.replaced_items[item] = dup_items
+            self.replaced_items[item] = list(dup_items)
             for dup_item in dup_items:
                 log.debug('replacing item %i: %s' %
                           (dup_item.id, displayable_path(item.path)))