Helm values cannot be overriden with null

.gitignore

templates/

Chart.yaml

apiVersion: v2
name: test-app

type: application
version: 0.0.0

output.txt

+ helm version
version.BuildInfo{Version:"v3.8.1", GitCommit:"5cb9af4b1b271d11d7a97a71df3ac337dd94ad37", GitTreeState:"", GoVersion:"go1.17.9"}
+ helm template .
---
# Source: test-app/templates/cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: release-name-parent-test-cm
  annotations:
    values.yaml: |
      test-value: null
      test-value-2: false
+ helm template . -f values.yaml
---
# Source: test-app/templates/cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: release-name-parent-test-cm
  annotations:
    values.yaml: |
      test-value-2: false
+ helm template . --set test-value=null
---
# Source: test-app/templates/cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: release-name-parent-test-cm
  annotations:
    values.yaml: |
      test-value-2: false
++ helm template .
+ diff -C5 /dev/fd/63 /dev/fd/62
++ helm template . -f values.yaml
*** /dev/fd/63	2022-04-29 13:00:33.941032907 +0200
--- /dev/fd/62	2022-04-29 13:00:33.941032907 +0200
***************
*** 4,10 ****
  kind: ConfigMap
  metadata:
    name: release-name-parent-test-cm
    annotations:
      values.yaml: |
-       test-value: null
        test-value-2: false
--- 4,9 ----

render.sh

#!/usr/bin/env bash
set -eEuo pipefail
mkdir -p templates

cat <<'EOF' > templates/cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ .Release.Name }}-parent-test-cm
  annotations:
    values.yaml: |
      {{- .Values | toYaml | nindent 6 }}
EOF

exec >output.txt 2>&1
set -x

helm version
helm template .
helm template . -f values.yaml
helm template . --set test-value=null

diff -C5 <(helm template .) <(helm template . -f values.yaml)

values.yaml

test-value: null
test-value-2: false