diff --git a/spinn_utilities/progress_bar.py b/spinn_utilities/progress_bar.py
index 3b4e3ebe..7c062bcd 100644
--- a/spinn_utilities/progress_bar.py
+++ b/spinn_utilities/progress_bar.py
@@ -13,12 +13,13 @@
 # limitations under the License.
 
 from collections import defaultdict
+from collections.abc import Sized
 from datetime import date
 import logging
 import math
 import os
 import sys
-from typing import Dict, Iterable, List, TypeVar
+from typing import Dict, Iterable, List, TypeVar, Union
 from spinn_utilities.config_holder import get_config_bool
 from spinn_utilities.log import FormatAdapter
 from spinn_utilities.overrides import overrides
@@ -46,15 +47,14 @@ class ProgressBar(object):
         "_step_character", "_end_character", "_in_bad_terminal",
     )
 
-    def __init__(self, total_number_of_things_to_do,
+    def __init__(self, total_number_of_things_to_do: Union[int, Sized],
                  string_describing_what_being_progressed,
                  step_character="=", end_character="|"):
         try:
             self._number_of_things = int(total_number_of_things_to_do)
         except TypeError:
 
-            # Might be dealing with general iterable; better not be infinite
-            self._number_of_things = len(list(total_number_of_things_to_do))
+            self._number_of_things = len(total_number_of_things_to_do)
 
         self._currently_completed = 0
         self._chars_per_thing = None