diff --git a/modoboa/admin/api/v2/serializers.py b/modoboa/admin/api/v2/serializers.py
index a6d2c0e06..e1310ebf9 100644
--- a/modoboa/admin/api/v2/serializers.py
+++ b/modoboa/admin/api/v2/serializers.py
@@ -540,7 +540,7 @@ class WritableAccountSerializer(v1_serializers.WritableAccountSerializer):
             instance.set_password(password)
         if mailbox_data:
             creator = self.context["request"].user
-            if hasattr(instance, "mailbox") and "mailbox" in validated_data:
+            if hasattr(instance, "mailbox"):
                 if "username" in validated_data:
                     mailbox_data["email"] = validated_data["username"]
                     instance.email = validated_data["username"]
diff --git a/modoboa/core/tests/test_views.py b/modoboa/core/tests/test_views.py
index 1c14f2d8f..19fbb306c 100644
--- a/modoboa/core/tests/test_views.py
+++ b/modoboa/core/tests/test_views.py
@@ -93,6 +93,20 @@ SETTINGS_SAMPLE = {
     "maillog-logfile": "/var/log/mail.log",
     "maillog-rrd_rootdir": "/tmp",
     "maillog-greylist": False,
+    "pdfcredentials-enabled_pdfcredentials": True,
+    "pdfcredentials-storage_dir": "./",
+    "pdfcredentials-delete_first_dl": True,
+    "pdfcredentials-generate_at_creation": True,
+    "pdfcredentials-title": "Modoboa",
+    "pdfcredentials-webpanel_url": "local.host/",
+    "pdfcredentials-custom_message": "test",
+    "pdfcredentials-include_connection_settings": False,
+    "pdfcredentials-smtp_server_address": "127.0.0.1",
+    "pdfcredentials-smtp_server_port": 666,
+    "pdfcredentials-smtp_connection_security": "starttls",
+    "pdfcredentials-imap_server_address": "127.0.0.1",
+    "pdfcredentials-imap_server_port": 667,
+    "pdfcredentials-imap_connection_security": "starttls"
 }
 
 
diff --git a/modoboa/lib/tests/__init__.py b/modoboa/lib/tests/__init__.py
index 608197a41..eda6d56bf 100644
--- a/modoboa/lib/tests/__init__.py
+++ b/modoboa/lib/tests/__init__.py
@@ -1,6 +1,7 @@
 """Testing utilities."""
 
 import socket
+import tempfile
 
 from django.conf import settings
 from django.core import management
@@ -65,6 +66,8 @@ class ModoTestCase(ParametersMixin, TestCase):
         """Initiate test context."""
         self.assertEqual(
             self.client.login(username=username, password=password), True)
+        self.workdir = tempfile.mkdtemp()
+        self.set_global_parameter("storage_dir", self.workdir, app="pdfcredentials")
 
     def ajax_request(self, method, url, params=None, status=200):
         if params is None:
@@ -102,6 +105,8 @@ class ModoAPITestCase(ParametersMixin, APITestCase):
         """Setup."""
         super(ModoAPITestCase, self).setUp()
         self.client.credentials(HTTP_AUTHORIZATION="Token " + self.token.key)
+        self.workdir = tempfile.mkdtemp()
+        self.set_global_parameter("storage_dir", self.workdir, app="pdfcredentials")
 
     def create_session(self):
         """Enable session storage across requests."""
diff --git a/modoboa/parameters/api/v2/tests.py b/modoboa/parameters/api/v2/tests.py
index 0803b650d..33cf993be 100644
--- a/modoboa/parameters/api/v2/tests.py
+++ b/modoboa/parameters/api/v2/tests.py
@@ -11,8 +11,8 @@ class ParametersAPITestCase(ModoAPITestCase):
         url = reverse("v2:parameter-applications")
         resp = self.client.get(url)
         self.assertEqual(resp.status_code, 200)
-        # core, admin, limits
-        self.assertEqual(len(resp.json()), 3)
+        # core, admin, limits, pdf credentials
+        self.assertEqual(len(resp.json()), 4)
 
     def test_get_structure(self):
         url = reverse("v2:parameter-structure")
diff --git a/modoboa/pdfcredentials/api/v2/tests.py b/modoboa/pdfcredentials/api/v2/tests.py
index c970eaf9a..aa5cf5391 100644
--- a/modoboa/pdfcredentials/api/v2/tests.py
+++ b/modoboa/pdfcredentials/api/v2/tests.py
@@ -1,6 +1,5 @@
 """API v2 tests."""
 
-import tempfile
 import shutil
 import os
 
@@ -20,12 +19,6 @@ class PDFCredentialViewTestCase(ModoAPITestCase):
         super().setUpTestData()
         factories.populate_database()
 
-    def setUp(self):
-        """Create temp. directory to store files."""
-        super().setUp()
-        self.workdir = tempfile.mkdtemp()
-        self.set_global_parameter("storage_dir", self.workdir)
-
     def tearDown(self):
         """Reset test env."""
         shutil.rmtree(self.workdir)