source-controller: Unable to clone gitlab private GitRepository with libgit2

Hello. I have a GitRepository poitning to a private repo with private keys (with write permissions) included:

apiVersion: source.toolkit.fluxcd.io/v1beta1
kind: GitRepository
metadata:
  name: cnm-dep
spec:
  interval: 24h
  url: ssh://git@my.gitlab/jj/cnm-dep.git
  secretRef:
    name: gitlab-key
  ref:
    branch: master

This works as expected, reconciles itself, no problem with updating corresponding Kustomization resource. However, image automation controller is unable to clone this repository when ImagePolicy is met. ImageUpdateAutomation resource is the following:

apiVersion: image.toolkit.fluxcd.io/v1beta1
kind: ImageUpdateAutomation
metadata:
  name: cnm-dep
spec:
  interval: 30s
  sourceRef:
    kind: GitRepository
    name: cnm-dep
  git:
    checkout:
      ref:
        branch: master
    commit:
      author:
        email: ml3k@interia.pl
        name: fluxcd
      messageTemplate: |
        (FluxCD) Update images
        {{range .Updated.Images}}
        - {{ . }}
        {{end}}
    push:
      branch: master
  update:
    path: ./
    strategy: Setters

Logs from image-automation-controller:

{"level":"error","ts":"2021-08-13T12:49:40.933Z","logger":"controller-runtime.manager.controller.imageupdateautomation","msg":"Reconciler error","reconciler group":"image.toolkit.fluxcd.io","reconciler kind":"ImageUpdateAutomation","name":"cnm-dep","namespace":"cnm","error":"unable to clone 'ssh://git@my.gitlab/jj/cnm-dep.git', error: Certificate"}

Identical configuration works as expected for github private repositories in the same cluster. Version i run is ghcr.io/fluxcd/image-automation-controller:v0.14.0.

Thank you in advance.