diff --git a/src/documents/models.py b/src/documents/models.py
index 89a9f5968..69d508350 100644
--- a/src/documents/models.py
+++ b/src/documents/models.py
@@ -326,6 +326,8 @@ class Document(models.Model):
     def generate_source_filename(self):
         # Create filename based on configured format
         if settings.PAPERLESS_FILENAME_FORMAT is not None:
+            tag = defaultdict(lambda: slugify(None),
+                              self.many_to_dictionary(self.tags))
             list_length = 10
             tags = self.many_to_list(self.tags)
             while True:
@@ -336,7 +338,7 @@ class Document(models.Model):
                            title=slugify(self.title),
                            created=slugify(self.created),
                            added=slugify(self.added),
-                           tag=defaultdict(str, self.many_to_dictionary(self.tags)),
+                           tag=tag,
                            tags=tags)
                     break
                 except IndexError:
diff --git a/src/documents/tests/test_file_handling.py b/src/documents/tests/test_file_handling.py
index fb7f152fc..3065948ea 100644
--- a/src/documents/tests/test_file_handling.py
+++ b/src/documents/tests/test_file_handling.py
@@ -206,7 +206,7 @@ class TestDate(TestCase):
         # Ensure that filename is properly generated
         tmp = document.source_filename
         self.assertEqual(document.generate_source_filename(),
-                         "0000001.pdf")
+                         "none-0000001.pdf")
         document.create_source_directory()
         Path(document.source_path).touch()