diff --git a/pyproject.toml b/pyproject.toml
index 73da25c..5581046 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,7 +37,7 @@ docs = [
 ]
 mypy = ["mypy==1.20.2"]
 pyright = ["basedpyright==1.39.3"]
-ruff = ["ruff==0.14.14"]
+ruff = ["ruff==0.15.12"]
 tests = [
     "coverage>=7.6.12",
     "pytest>=8.3.4",
diff --git a/src/brreg/enhetsregisteret/_types.py b/src/brreg/enhetsregisteret/_types.py
index 6752185..b2735fc 100644
--- a/src/brreg/enhetsregisteret/_types.py
+++ b/src/brreg/enhetsregisteret/_types.py
@@ -9,7 +9,7 @@
 CommaList = Annotated[
     list[T],
     PlainSerializer(
-        lambda v: ",".join(v),
+        ",".join,
         return_type=str,
         when_used="json",
     ),