diff --git a/requirements/base.txt b/requirements/base.txt
index 77478745d..9778b69a8 100644
--- a/requirements/base.txt
+++ b/requirements/base.txt
@@ -28,7 +28,7 @@ alembic==1.12.1
 aniso8601==9.0.1
     # via coaster
 anyio==4.0.0
-    # via httpcore
+    # via httpx
 argon2-cffi==23.1.0
     # via -r requirements/base.in
 argon2-cffi-bindings==21.2.0
@@ -55,15 +55,15 @@ bleach==6.1.0
     # via
     #   baseframe
     #   coaster
-blinker==1.6.3
+blinker==1.7.0
     # via
     #   -r requirements/base.in
     #   baseframe
     #   coaster
     #   flask
-boto3==1.28.72
+boto3==1.28.83
     # via -r requirements/base.in
-botocore==1.31.72
+botocore==1.31.83
     # via
     #   boto3
     #   s3transfer
@@ -83,7 +83,7 @@ cffi==1.16.0
     # via
     #   argon2-cffi-bindings
     #   cryptography
-charset-normalizer==3.3.1
+charset-normalizer==3.3.2
     # via
     #   aiohttp
     #   requests
@@ -114,7 +114,7 @@ dnspython==2.4.2
     #   pyisemail
 emoji==2.8.0
     # via baseframe
-filelock==3.12.4
+filelock==3.13.1
     # via tldextract
 flask==3.0.0
     # via
@@ -146,9 +146,9 @@ flask-caching==2.1.0
     # via baseframe
 flask-executor==1.0.0
     # via -r requirements/base.in
-flask-flatpages==0.8.1
+flask-flatpages==0.8.2
     # via -r requirements/base.in
-flask-mailman==0.3.0
+flask-mailman==1.0.0
     # via -r requirements/base.in
 flask-migrate==4.0.5
     # via
@@ -202,19 +202,19 @@ html5lib==1.1
     # via
     #   baseframe
     #   coaster
-httpcore==0.18.0
+httpcore==1.0.1
     # via httpx
 httplib2==0.22.0
     # via
     #   oauth2
     #   oauth2client
-httpx[http2]==0.25.0
+httpx[http2]==0.25.1
     # via
     #   -r requirements/base.in
     #   python-telegram-bot
 hyperframe==6.0.1
     # via h2
-icalendar==5.0.10
+icalendar==5.0.11
     # via -r requirements/base.in
 idna==3.4
     # via
@@ -248,9 +248,9 @@ linkify-it-py==2.0.2
     # via -r requirements/base.in
 lxml==4.9.3
     # via premailer
-mako==1.2.4
+mako==1.3.0
     # via alembic
-markdown==3.5
+markdown==3.5.1
     # via
     #   coaster
     #   flask-flatpages
@@ -270,14 +270,12 @@ markupsafe==2.1.3
     #   wtforms
 marshmallow==3.20.1
     # via dataclasses-json
-maxminddb==2.4.0
+maxminddb==2.5.1
     # via geoip2
 mdit-py-plugins==0.4.0
     # via -r requirements/base.in
 mdurl==0.1.2
     # via markdown-it-py
-mkdocs-material-extensions==1.3
-    # via flask-mailman
 multidict==6.0.4
     # via
     #   aiohttp
@@ -304,7 +302,7 @@ packaging==23.2
     #   marshmallow
 passlib==1.7.4
     # via -r requirements/base.in
-phonenumbers==8.13.23
+phonenumbers==8.13.24
     # via -r requirements/base.in
 premailer==3.10.0
     # via -r requirements/base.in
@@ -425,7 +423,7 @@ semantic-version==2.10.0
     # via
     #   baseframe
     #   coaster
-sentry-sdk==1.32.0
+sentry-sdk==1.34.0
     # via baseframe
 six==1.16.0
     # via
@@ -442,9 +440,8 @@ six==1.16.0
 sniffio==1.3.0
     # via
     #   anyio
-    #   httpcore
     #   httpx
-sqlalchemy==2.0.22
+sqlalchemy==2.0.23
     # via
     #   -r requirements/base.in
     #   alembic
@@ -463,7 +460,7 @@ statsd==4.0.1
     # via baseframe
 tinydb==4.8.0
     # via tuspy
-tldextract==5.0.1
+tldextract==5.1.0
     # via
     #   coaster
     #   mxsniff
@@ -475,7 +472,7 @@ tuspy==1.0.1
     # via pyvimeo
 tweepy==4.14.0
     # via -r requirements/base.in
-twilio==8.10.0
+twilio==8.10.1
     # via -r requirements/base.in
 types-python-dateutil==2.8.19.14
     # via arrow
@@ -524,7 +521,7 @@ werkzeug==3.0.1
     #   flask
 whitenoise==6.6.0
     # via -r requirements/base.in
-wtforms==3.1.0
+wtforms==3.1.1
     # via
     #   baseframe
     #   flask-wtf
diff --git a/requirements/test.txt b/requirements/test.txt
index facf4d46e..3f0798f76 100644
--- a/requirements/test.txt
+++ b/requirements/test.txt
@@ -64,9 +64,9 @@ pytest-cov==4.1.0
     # via -r requirements/test.in
 pytest-dotenv==0.5.2
     # via -r requirements/test.in
-pytest-env==1.1.0
+pytest-env==1.1.1
     # via -r requirements/test.in
-pytest-html==4.0.2
+pytest-html==4.1.1
     # via pytest-selenium
 pytest-metadata==3.0.0
     # via pytest-html
@@ -94,9 +94,9 @@ sttable==0.0.1
     # via -r requirements/test.in
 tenacity==8.2.3
     # via pytest-selenium
-tomlkit==0.12.1
+tomlkit==0.12.2
     # via -r requirements/test.in
-trio==0.22.2
+trio==0.23.1
     # via
     #   selenium
     #   trio-websocket
diff --git a/tests/unit/views/preview_image_test.py b/tests/unit/views/preview_image_test.py
index b037a8f6d..2c2dc438e 100644
--- a/tests/unit/views/preview_image_test.py
+++ b/tests/unit/views/preview_image_test.py
@@ -1,5 +1,6 @@
 import pytest
 import io
+from magic import from_buffer
 from PIL import Image
 
 from funnel.views.thumbnails import render_project_preview_image
@@ -14,5 +15,6 @@ def test_preview_image_jobs(project_expo2011) -> None:
 def test_preview_image_size(project_expo2011) -> None:
     render_project_preview_image(project_id=project_expo2011.id)
     preview_image = Image.open(io.BytesIO(project_expo2011.preview_image))
+    result = from_buffer(io.BytesIO(project_expo2011.preview_image).read(2048), mime=True)
     assert preview_image.size == (1280, 720)
-    assert preview_image.format is 'PNG'
+    assert result == 'image/png'