diff --git a/lib/galaxy/webapps/galaxy/controllers/dataset.py b/lib/galaxy/webapps/galaxy/controllers/dataset.py
index 1df5bf93256..c73a29f1b30 100644
--- a/lib/galaxy/webapps/galaxy/controllers/dataset.py
+++ b/lib/galaxy/webapps/galaxy/controllers/dataset.py
@@ -1000,7 +1000,7 @@ class DatasetInterface( BaseUIController, UsesAnnotations, UsesHistoryMixin, Use
         elif target_history_ids:
             if not isinstance( target_history_ids, list ):
                 target_history_ids = target_history_ids.split(",")
-            target_history_ids = set([ trans.security.decode_id(h) for h in target_history_ids if h ])
+            target_history_ids = list(set([ trans.security.decode_id(h) for h in target_history_ids if h ]))
         else:
             target_history_ids = []
         done_msg = error_msg = ""