diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a599b737..06bf77bb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -428,7 +428,7 @@ locales:
 
 black:
   stage: lint
-  image: debian:bookworm-slim
+  image: debian:trixie-slim
   <<: *apt-template
   script:
     - apt-get install black
diff --git a/tests/test_build.py b/tests/test_build.py
index 578837ed..56322b14 100755
--- a/tests/test_build.py
+++ b/tests/test_build.py
@@ -613,9 +613,9 @@ class BuildTest(unittest.TestCase):
         with open(metadata_file) as fp:
             app = fdroidserver.metadata.App(yaml.safe_load(fp))
         app['RepoType'] = 'git'
-        app[
-            'Binaries'
-        ] = 'https://example.com/fdroid/repo/info.guardianproject.checkey_%v.apk'
+        app['Binaries'] = (
+            'https://example.com/fdroid/repo/info.guardianproject.checkey_%v.apk'
+        )
         build = fdroidserver.metadata.Build(
             {
                 'versionCode': 123,
@@ -703,9 +703,9 @@ class BuildTest(unittest.TestCase):
         with open(metadata_file) as fp:
             app = fdroidserver.metadata.App(yaml.safe_load(fp))
         app['RepoType'] = 'git'
-        app[
-            'Binaries'
-        ] = 'https://example.com/fdroid/repo/info.guardianproject.checkey_%v.apk'
+        app['Binaries'] = (
+            'https://example.com/fdroid/repo/info.guardianproject.checkey_%v.apk'
+        )
         build = fdroidserver.metadata.Build(
             {
                 'versionCode': 123,
diff --git a/tests/test_metadata.py b/tests/test_metadata.py
index 5a3ee8ef..b56adf32 100755
--- a/tests/test_metadata.py
+++ b/tests/test_metadata.py
@@ -309,7 +309,9 @@ class MetadataTest(unittest.TestCase):
     def test_metadata_overrides_dot_fdroid_yml(self):
         """Fields in metadata files should override anything in .fdroid.yml."""
         app = metadata.parse_metadata('metadata/info.guardianproject.urzip.yml')
-        self.assertEqual(app['Summary'], '一个实用工具，获取已安装在您的设备上的应用的有关信息')
+        self.assertEqual(
+            app['Summary'], '一个实用工具，获取已安装在您的设备上的应用的有关信息'
+        )
 
     def test_dot_fdroid_yml_works_without_git(self):
         """Parsing should work if .fdroid.yml is present and it is not a git repo."""
@@ -487,9 +489,9 @@ class MetadataTest(unittest.TestCase):
         yamldata = dict()
         metadata.post_parse_yaml_metadata(yamldata)
 
-        yamldata[
-            'AllowedAPKSigningKeys'
-        ] = 'c03dac71394d6c26766f1b04d3e31cfcac5d03b55d8aa40cc9b9fa6b74354c66'
+        yamldata['AllowedAPKSigningKeys'] = (
+            'c03dac71394d6c26766f1b04d3e31cfcac5d03b55d8aa40cc9b9fa6b74354c66'
+        )
         metadata.post_parse_yaml_metadata(yamldata)
 
     def test_post_parse_yaml_metadata_ArchivePolicy_int(self):
@@ -2076,7 +2078,7 @@ class MetadataTest(unittest.TestCase):
         self.assertEqual(
             metadata._format_stringmap('🔥', 'test', {'NonFree': {}, 'Ads': {'en': ''}}),
             ['Ads', 'NonFree'],
-        )
+        )  # fmt: skip
 
     def test_format_stringmap_three_list(self):
         self.assertEqual(
diff --git a/tests/test_publish.py b/tests/test_publish.py
index 82c670d7..cc1b3459 100755
--- a/tests/test_publish.py
+++ b/tests/test_publish.py
@@ -205,9 +205,9 @@ class PublishTest(unittest.TestCase):
         publish.config['keystorepass'] = '123456'
         publish.config['keypass'] = '654321'
         publish.config['keystore'] = "keystore.jks"
-        publish.config[
-            'keydname'
-        ] = 'CN=Birdman, OU=Cell, O=Alcatraz, L=Alcatraz, S=CA, C=US'
+        publish.config['keydname'] = (
+            'CN=Birdman, OU=Cell, O=Alcatraz, L=Alcatraz, S=CA, C=US'
+        )
         os.chdir(self.testdir)
         keystore = jks.KeyStore.new("jks", [])
         keystore.save(publish.config['keystore'], publish.config['keystorepass'])