diff --git a/README.md b/README.md
index 340752ca7..74501784e 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ GOV.UK Notify admin application - https://www.notifications.service.gov.uk/
 
 ### Python version
 
-At the moment we run Python 3.6 in production.
+At the moment we run Python 3.9 in production.
 
 ### NPM packages
 
diff --git a/requirements.txt b/requirements.txt
index 84e2947c5..879079b9d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with python 3.6
+# This file is autogenerated by pip-compile with python 3.9
 # To update, run:
 #
 #    pip-compile requirements.in
@@ -43,8 +43,6 @@ cryptography==3.3.2
     # via
     #   -r requirements.in
     #   fido2
-dataclasses==0.8
-    # via werkzeug
 dnspython==1.16.0
     # via eventlet
 docopt==0.6.2
@@ -90,10 +88,7 @@ humanize==3.12.0
 idna==2.10
     # via requests
 importlib-metadata==4.2.0
-    # via
-    #   -r requirements.in
-    #   click
-    #   humanize
+    # via -r requirements.in
 itsdangerous==1.1.0
     # via
     #   -r requirements.in
@@ -215,8 +210,6 @@ statsd==3.3.0
     # via notifications-utils
 texttable==1.6.3
     # via pyexcel
-typing-extensions==3.10.0.0
-    # via importlib-metadata
 urllib3==1.26.5
     # via
     #   botocore
diff --git a/runtime.txt b/runtime.txt
index 62ce9c02a..305091cae 100644
--- a/runtime.txt
+++ b/runtime.txt
@@ -1 +1 @@
-python-3.6.x
+python-3.9.x
diff --git a/tests/app/test_template_previews.py b/tests/app/test_template_previews.py
index 37554be34..1954c3c9d 100644
--- a/tests/app/test_template_previews.py
+++ b/tests/app/test_template_previews.py
@@ -5,6 +5,7 @@ from unittest.mock import Mock
 import pytest
 from notifications_utils.template import LetterPreviewTemplate
 
+from app import load_service_before_request
 from app.template_previews import (
     TemplatePreview,
     get_page_count_for_letter,
@@ -58,6 +59,10 @@ def test_from_database_object_makes_request(
     expected_filename,
     mock_get_service_letter_template
 ):
+    # This test is calling `current_service` outside a Flask endpoint, so we need to make sure
+    # `service` is in the `_request_ctx_stack` to avoid an error
+    load_service_before_request()
+
     resp = Mock(content='a', status_code='b', headers={'c': 'd'})
     request_mock = mocker.patch('app.template_previews.requests.post', return_value=resp)
     mocker.patch('app.template_previews.current_service', letter_branding=letter_branding)