diff --git a/app/__init__.py b/app/__init__.py
index 8e774cccb..a21b8546a 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -211,7 +211,7 @@ def create_uuid():
 
 
 def create_random_identifier():
-    return ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(16))
+    return ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(16))
 
 
 def process_user_agent(user_agent_string):
diff --git a/tests/app/celery/test_tasks.py b/tests/app/celery/test_tasks.py
index 0a960329b..adc8f7184 100644
--- a/tests/app/celery/test_tasks.py
+++ b/tests/app/celery/test_tasks.py
@@ -1044,9 +1044,7 @@ def test_create_dvla_file_contents(sample_letter_template, mocker):
 def test_dvla_letter_template(sample_letter_notification):
     t = {"content": sample_letter_notification.template.content,
          "subject": sample_letter_notification.template.subject}
-    letter = LetterDVLATemplate(t,
-                                sample_letter_notification.personalisation,
-                                "random-string")
+    letter = LetterDVLATemplate(t, sample_letter_notification.personalisation, "random-string")
     assert str(letter) == "140|500|001||random-string|||||||||||||A1||A2|A3|A4|A5|A6|A_POST|||||||||23 March 2017<cr><cr><h1>Template subject<normal><cr><cr>Dear Sir/Madam, Hello. Yours Truly, The Government.<cr><cr>"  # noqa