diff --git a/.github/prtester.py b/.github/prtester.py
index aa0eef20..8938923a 100644
--- a/.github/prtester.py
+++ b/.github/prtester.py
@@ -142,7 +142,7 @@ def testBridges(instance: Instance, bridge_cards: Iterable, with_upload: bool, w
                     status = '✔️'
                 if with_upload and (not with_reduced_upload or not status_is_ok):
                     filename = f'{os.getcwd()}/{instance.name}_{form_number}.html'
-                    with open(file=filename, mode='wb', encoding='utf-8') as file:
+                    with open(file=filename, mode='wb') as file:
                         file.write(page_text)
             table_rows.append(f'| {bridge_name} | [{form_number} {context_name}{instance_suffix}]({tester_url}) | {status} |')
             form_number += 1