diff --git a/src/twomartens/masterthesis/ssd.py b/src/twomartens/masterthesis/ssd.py
index ac55d24..b45e3fc 100644
--- a/src/twomartens/masterthesis/ssd.py
+++ b/src/twomartens/masterthesis/ssd.py
@@ -219,9 +219,9 @@ def _predict_one_epoch(dataset: tf.data.Dataset,
         all_objects = muppy.get_objects()
         all_lists = muppy.filter(all_objects, Type=list)
         if lists is None:
-            lists = set(all_lists)
+            lists = set(map(tuple, all_lists))
         else:
-            all_lists = set(all_lists)
+            all_lists = set(map(tuple, all_lists))
             print(all_lists.difference(lists))
     
     epoch_end_time = time.time()