grype not using custom config.yaml

Question

I use grype security scanner to scan my docker image. I run grype itself also as docker container with the following command:

docker run -v ./grype-config:/config -e "DOCKER_CONFIG=/config" anchore/grype:latest -c "/config/config.yaml" my-own-image

In the current directoy a have a sub directory grype-config which contains the file config.yaml which has the following content:

# the output format of the vulnerability report (options: table, json, cyclonedx)
# same as -o ; GRYPE_OUTPUT env var
output: "json"

ignore:
  # We can make rules to match just by vulnerability ID:
  - vulnerability: CVE-2023-5156
  - vulnerability: CVE-2023-4813
  - vulnerability: CVE-2023-4806
  - vulnerability: CVE-2016-20013
  - vulnerability: CVE-2022-27943
  - vulnerability: CVE-2022-27943

The output from grype is the following:

NAME        INSTALLED              FIXED-IN  TYPE  VULNERABILITY   SEVERITY
libc6       2.35-0ubuntu3.4                  deb   CVE-2023-5156   Medium
libc6       2.35-0ubuntu3.4                  deb   CVE-2023-4813   Low
libc6       2.35-0ubuntu3.4                  deb   CVE-2023-4806   Low
libc6       2.35-0ubuntu3.4                  deb   CVE-2016-20013  Negligible
libgcc-s1   12.3.0-1ubuntu1~22.04            deb   CVE-2022-27943  Low
libstdc++6  12.3.0-1ubuntu1~22.04            deb   CVE-2022-27943  Low

Obviously grype ignores my config.yaml as it uses the output format table, not the output format json set in config.yaml

Does anyone know how to fix this?