diff --git a/app/letter_branding/letter_branding_schema.py b/app/letter_branding/letter_branding_schema.py
index d6275c82d..3c7acb7b0 100644
--- a/app/letter_branding/letter_branding_schema.py
+++ b/app/letter_branding/letter_branding_schema.py
@@ -6,5 +6,5 @@ post_letter_branding_schema = {
         "name": {"type": ["string", "null"]},
         "filename": {"type": ["string", "null"]},
     },
-    "required": ("name", "filename")
+    "required": ["name", "filename"]
 }
diff --git a/requirements.in b/requirements.in
index 9d4ede6d9..d920aa8e4 100644
--- a/requirements.in
+++ b/requirements.in
@@ -13,13 +13,13 @@ click-datetime==0.2
 git+https://github.com/benoitc/gunicorn.git@1299ea9e967a61ae2edebe191082fd169b864c64#egg=gunicorn[eventlet]==20.1.0
 iso8601==1.0.2
 itsdangerous==2.1.2
-jsonschema==3.2.0
+jsonschema==4.4.0
 marshmallow-sqlalchemy==0.23.1 # pyup: <0.24.0 # marshmallow v3 throws errors
 marshmallow==2.21.0 # pyup: <3 # v3 throws errors
 psycopg2-binary==2.9.3
 PyJWT==2.3.0
 SQLAlchemy==1.4.35
-strict-rfc3339==0.7
+rfc3339-validator==0.1.4
 rfc3987==1.3.8
 cachetools==5.0.0
 beautifulsoup4==4.10.0
diff --git a/requirements.txt b/requirements.txt
index c3c3dd044..c6a820a2d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -123,7 +123,7 @@ jmespath==0.10.0
     # via
     #   boto3
     #   botocore
-jsonschema==3.2.0
+jsonschema==4.4.0
     # via -r requirements.in
 kombu==5.2.3
     # via celery
@@ -200,6 +200,8 @@ requests==2.26.0
     #   govuk-bank-holidays
     #   notifications-python-client
     #   notifications-utils
+rfc3339-validator==0.1.4
+    # via -r requirements.in
 rfc3987==1.3.8
     # via -r requirements.in
 rsa==4.7.2
@@ -218,8 +220,8 @@ six==1.16.0
     #   click-repl
     #   eventlet
     #   flask-marshmallow
-    #   jsonschema
     #   python-dateutil
+    #   rfc3339-validator
 smartypants==2.0.1
     # via notifications-utils
 soupsieve==2.2.1
@@ -231,8 +233,6 @@ sqlalchemy==1.4.35
     #   marshmallow-sqlalchemy
 statsd==3.3.0
     # via notifications-utils
-strict-rfc3339==0.7
-    # via -r requirements.in
 urllib3==1.26.7
     # via
     #   botocore
diff --git a/tests/app/complaint/test_complaint_rest.py b/tests/app/complaint/test_complaint_rest.py
index ea44ca636..5f72e4ee2 100644
--- a/tests/app/complaint/test_complaint_rest.py
+++ b/tests/app/complaint/test_complaint_rest.py
@@ -87,5 +87,4 @@ def test_get_complaint_with_invalid_data_returns_400_status_code(client):
     )
 
     assert response.status_code == 400
-    assert response.json['errors'][0]['message'] == 'start_date time data {} does not match format %Y-%m-%d'.format(
-        start_date)
+    assert response.json['errors'][0]['message'] == 'start_date month must be in 1..12'
diff --git a/tests/app/platform_stats/test_rest.py b/tests/app/platform_stats/test_rest.py
index 27ba169e0..eda62b1dd 100644
--- a/tests/app/platform_stats/test_rest.py
+++ b/tests/app/platform_stats/test_rest.py
@@ -48,8 +48,7 @@ def test_get_platform_stats_validates_the_date(admin_request):
         _expected_status=400
     )
 
-    assert response['errors'][0]['message'] == 'start_date time data {} does not match format %Y-%m-%d'.format(
-        start_date)
+    assert response['errors'][0]['message'] == 'start_date month must be in 1..12'
 
 
 @freeze_time('2018-10-31 14:00')