diff --git a/.gitignore b/.gitignore
index e4f8ff58e..191965988 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@ __pycache__/
 *.py[cod]
 
 venv/
+venv-freeze/
 
 # C extensions
 *.so
diff --git a/app/letters/utils.py b/app/letters/utils.py
index c14cc80d1..a293663c1 100644
--- a/app/letters/utils.py
+++ b/app/letters/utils.py
@@ -135,14 +135,15 @@ def get_letter_pdf(notification):
     s3 = boto3.resource('s3')
     bucket = s3.Bucket(bucket_name)
 
-    for item in bucket.objects.filter(Prefix=get_bucket_prefix_for_notification(notification, is_test_letter)):
-        obj = s3.Object(
-            bucket_name=bucket_name,
-            key=item.key
-        )
-        file_content = obj.get()["Body"].read()
+    item = next(x for x in bucket.objects.filter(
+        Prefix=get_bucket_prefix_for_notification(notification, is_test_letter)
+    ))
 
-    return file_content
+    obj = s3.Object(
+        bucket_name=bucket_name,
+        key=item.key
+    )
+    return obj.get()["Body"].read()
 
 
 def _move_s3_object(source_bucket, source_filename, target_bucket, target_filename):
diff --git a/requirements-app.txt b/requirements-app.txt
index 613e31c88..500f01f06 100644
--- a/requirements-app.txt
+++ b/requirements-app.txt
@@ -5,7 +5,7 @@ cffi==1.11.5
 celery==3.1.26.post2 # pyup: <4
 docopt==0.6.2
 Flask-Bcrypt==0.7.1
-flask-marshmallow==0.8.0
+flask-marshmallow==0.9.0
 Flask-Migrate==2.2.1
 Flask-SQLAlchemy==2.3.2
 Flask==1.0.2
@@ -15,16 +15,16 @@ gunicorn==19.7.1
 iso8601==0.1.12
 jsonschema==2.6.0
 marshmallow-sqlalchemy==0.14.0
-marshmallow==2.15.3
+marshmallow==2.15.4
 psycopg2-binary==2.7.5
 PyJWT==1.6.4
-SQLAlchemy==1.2.9
+SQLAlchemy==1.2.10
 
-notifications-python-client==4.8.2
+notifications-python-client==5.0.0
 
 # PaaS
 awscli-cwlogs>=1.4,<1.5
 
-git+https://github.com/alphagov/notifications-utils.git@29.3.4#egg=notifications-utils==29.3.4
+git+https://github.com/alphagov/notifications-utils.git@29.3.5#egg=notifications-utils==29.3.5
 
 git+https://github.com/alphagov/boto.git@2.43.0-patch3#egg=boto==2.43.0-patch3
diff --git a/requirements.txt b/requirements.txt
index 61a7ff250..1d69a09bd 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,7 +7,7 @@ cffi==1.11.5
 celery==3.1.26.post2 # pyup: <4
 docopt==0.6.2
 Flask-Bcrypt==0.7.1
-flask-marshmallow==0.8.0
+flask-marshmallow==0.9.0
 Flask-Migrate==2.2.1
 Flask-SQLAlchemy==2.3.2
 Flask==1.0.2
@@ -17,17 +17,17 @@ gunicorn==19.7.1
 iso8601==0.1.12
 jsonschema==2.6.0
 marshmallow-sqlalchemy==0.14.0
-marshmallow==2.15.3
+marshmallow==2.15.4
 psycopg2-binary==2.7.5
 PyJWT==1.6.4
-SQLAlchemy==1.2.9
+SQLAlchemy==1.2.10
 
-notifications-python-client==4.8.2
+notifications-python-client==5.0.0
 
 # PaaS
 awscli-cwlogs>=1.4,<1.5
 
-git+https://github.com/alphagov/notifications-utils.git@29.3.4#egg=notifications-utils==29.3.4
+git+https://github.com/alphagov/notifications-utils.git@29.3.5#egg=notifications-utils==29.3.5
 
 git+https://github.com/alphagov/boto.git@2.43.0-patch3#egg=boto==2.43.0-patch3
 
@@ -35,12 +35,12 @@ git+https://github.com/alphagov/boto.git@2.43.0-patch3#egg=boto==2.43.0-patch3
 alembic==1.0.0
 amqp==1.4.9
 anyjson==0.3.3
-awscli==1.15.70
+awscli==1.15.74
 bcrypt==3.1.4
 billiard==3.3.0.23
 bleach==2.1.3
 boto3==1.6.16
-botocore==1.10.69
+botocore==1.10.73
 certifi==2018.4.16
 chardet==3.0.4
 click==6.7
diff --git a/requirements_for_test.txt b/requirements_for_test.txt
index b26445b34..1555e3d64 100644
--- a/requirements_for_test.txt
+++ b/requirements_for_test.txt
@@ -1,14 +1,14 @@
 -r requirements.txt
 flake8==3.5.0
 moto==1.3.3
-pytest==3.6.3
+pytest==3.7.1
 pytest-env==0.6.2
 pytest-mock==1.10.0
 pytest-cov==2.5.1
-pytest-xdist==1.22.2
+pytest-xdist==1.22.5
 coveralls==1.3.0
 freezegun==0.3.10
-requests-mock==1.5.0
+requests-mock==1.5.2
 # optional requirements for jsonschema
 strict-rfc3339==0.7
-rfc3987==1.3.7
+rfc3987==1.3.8
diff --git a/tests/app/letters/test_letter_utils.py b/tests/app/letters/test_letter_utils.py
index 8d5f5017c..2430c57cf 100644
--- a/tests/app/letters/test_letter_utils.py
+++ b/tests/app/letters/test_letter_utils.py
@@ -21,13 +21,13 @@ FROZEN_DATE_TIME = "2018-03-14 17:00:00"
 
 
 @pytest.fixture()
-@freeze_time(FROZEN_DATE_TIME)
 def sample_precompiled_letter_notification_using_test_key(sample_letter_notification):
     sample_letter_notification.template.hidden = True
     sample_letter_notification.template.name = PRECOMPILED_TEMPLATE_NAME
     sample_letter_notification.key_type = KEY_TYPE_TEST
     sample_letter_notification.reference = 'foo'
-    sample_letter_notification.created_at = datetime.utcnow()
+    with freeze_time(FROZEN_DATE_TIME):
+        sample_letter_notification.created_at = datetime.utcnow()
     return sample_letter_notification