diff --git a/requirements-app.txt b/requirements-app.txt
index 69bfec5a5..38a4f9cbf 100644
--- a/requirements-app.txt
+++ b/requirements-app.txt
@@ -29,7 +29,7 @@ notifications-python-client==5.7.0
 # PaaS
 awscli-cwlogs==1.4.6
 
-git+https://github.com/alphagov/notifications-utils.git@43.5.8#egg=notifications-utils==43.5.8
+git+https://github.com/alphagov/notifications-utils.git@43.5.9#egg=notifications-utils==43.5.9
 
 # gds-metrics requires prometheseus 0.2.0, override that requirement as 0.7.1 brings significant performance gains
 prometheus-client==0.8.0
diff --git a/requirements.txt b/requirements.txt
index bcaab1eb1..794dc2d75 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -31,7 +31,7 @@ notifications-python-client==5.7.0
 # PaaS
 awscli-cwlogs==1.4.6
 
-git+https://github.com/alphagov/notifications-utils.git@43.5.8#egg=notifications-utils==43.5.8
+git+https://github.com/alphagov/notifications-utils.git@43.5.9#egg=notifications-utils==43.5.9
 
 # gds-metrics requires prometheseus 0.2.0, override that requirement as 0.7.1 brings significant performance gains
 prometheus-client==0.8.0
diff --git a/tests/app/notifications/test_validators.py b/tests/app/notifications/test_validators.py
index df9b8c820..9df45b3ad 100644
--- a/tests/app/notifications/test_validators.py
+++ b/tests/app/notifications/test_validators.py
@@ -345,7 +345,7 @@ def test_check_is_message_too_long_fails(notify_db_session, show_prefix, char_co
 
 
 def test_check_is_message_too_long_passes_for_long_email(sample_service):
-    email_character_count = 2000003
+    email_character_count = 2_000_001
     t = create_template(service=sample_service, content='a' * email_character_count, template_type='email')
     template = templates_dao.dao_get_template_by_id_and_service_id(template_id=t.id,
                                                                    service_id=t.service_id)
@@ -357,7 +357,7 @@ def test_check_is_message_too_long_passes_for_long_email(sample_service):
     expected_message = (
         'Your message is too long. ' +
         'Emails cannot be longer than 2000000 bytes. ' +
-        'Your message is 2000084 bytes.'
+        'Your message is 2000001 bytes.'
     )
     assert e.value.message == expected_message
     assert e.value.fields == []