diff --git a/arkindex/project/serializer_fields.py b/arkindex/project/serializer_fields.py
index 230bafd37351cccedda4d2f0c8298f0b3cc1f916..06245b86fc0ef12f757846b56b71927b684d87bd 100644
--- a/arkindex/project/serializer_fields.py
+++ b/arkindex/project/serializer_fields.py
@@ -304,4 +304,4 @@ class NullField(serializers.CharField):
     def to_internal_value(self, data):
         if data is not None:
             self.fail("invalid")
-        return None
+        return
diff --git a/ruff.toml b/ruff.toml
index 477708d4306f4177dd74f0dc3fa2c081b932a718..749c24cac4220a4ad6b45c3db0ae3c6119e8625a 100644
--- a/ruff.toml
+++ b/ruff.toml
@@ -5,5 +5,8 @@ line-length = 120
 quote-style = "double"
 
 [lint]
-select = ["Q0", "F", "W", "E"]
+select = ["Q0", "F", "W", "E",
+    # flake8-return: unnecessary-return-none
+    "RET501",
+]
 ignore = ["E501"]