diff --git a/pyproject.toml b/pyproject.toml
index cde79074..17a30535 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,7 @@ build-backend = "setuptools.build_meta"
 [tool.setuptools_scm]
 # this is used populated when creating a git archive
 # and when there is .git dir and/or there is no git installed
-fallback_version = "9999.$Format:%h-%cs$"
+fallback_version = "9999.dev99"
 
 [tool.pytest.ini_options]
 norecursedirs = [
diff --git a/src/commoncode/resource.py b/src/commoncode/resource.py
index 1da2dc95..4280b841 100644
--- a/src/commoncode/resource.py
+++ b/src/commoncode/resource.py
@@ -1840,6 +1840,8 @@ def _populate(self, scan_data):
         ##########################################################
         for attr_name in self.codebase_attributes:
             value = scan_data.get(attr_name)
+            if value == None:
+                continue
             setattr(self.attributes, attr_name, value)
 
         ##########################################################
diff --git a/tests/test_resource.py b/tests/test_resource.py
index 907436d7..4e84523b 100644
--- a/tests/test_resource.py
+++ b/tests/test_resource.py
@@ -12,6 +12,8 @@
 from os.path import exists
 from os.path import join
 
+import attr
+
 from commoncode.fileutils import parent_directory
 from commoncode.resource import Codebase
 from commoncode.resource import Resource
@@ -661,6 +663,17 @@ def test_VirtualCodebase_with_paths_works(self):
         )
         check_against_expected_json_file(results, expected_file, regen=False)
 
+    def test_VirtualCodebase_codebase_attributes_assignment(self):
+        test_codebase = self.get_test_loc('resource/with_path/virtual-codebase.json')
+        vc = VirtualCodebase(
+            location=test_codebase,
+            codebase_attributes=dict(
+                packages=attr.ib(default=attr.Factory(list))
+            ),
+        )
+        self.assertNotEqual(vc.attributes.packages, None)
+        self.assertEqual(vc.attributes.packages, [])
+
 
 class TestCodebaseCache(FileBasedTesting):
     test_data_dir = join(dirname(__file__), 'data')