diff --git a/infra/docker-compose.yml b/infra/docker-compose.yml
index 3a5a6da..6ac6fae 100644
--- a/infra/docker-compose.yml
+++ b/infra/docker-compose.yml
@@ -57,6 +57,9 @@ services:
       # share this anchor and ignore it — they don't run uwsgi.
       UWSGI_PROCESSES: "1"
       UWSGI_THREADS: "2"
+      # Same lever for oz-celery: unset, the worker forks one process per CPU (22 on the lab node,
+      # ~225 MB each), which OOM-killed the shared runner mid-verify-stack. Only celery reads it.
+      CELERY_WORKER_CONCURRENCY: "2"
       DJANGO_SETTINGS_MODULE: openzaak.conf.docker
       SECRET_KEY: ${OZ_SECRET_KEY:-dev-only-not-for-production}
       DB_HOST: oz-db
@@ -144,6 +147,8 @@ services:
       # 1 uWSGI worker, not the image default of 4×4 (#147) — see the oz-env note above.
       UWSGI_PROCESSES: "1"
       UWSGI_THREADS: "2"
+      # Two celery workers, not one per CPU — see the oz-env note above.
+      CELERY_WORKER_CONCURRENCY: "2"
       DJANGO_SETTINGS_MODULE: nrc.conf.docker
       SECRET_KEY: ${NRC_SECRET_KEY:-dev-only-not-for-production}
       DB_HOST: nrc-db
diff --git a/infra/helm/big-reference/values.yaml b/infra/helm/big-reference/values.yaml
index 8b9c92e..1fb687f 100644
--- a/infra/helm/big-reference/values.yaml
+++ b/infra/helm/big-reference/values.yaml
@@ -82,6 +82,7 @@ envGroups:
   oz:
     UWSGI_PROCESSES: "1"
     UWSGI_THREADS: "2"
+    CELERY_WORKER_CONCURRENCY: "2"
     DJANGO_SETTINGS_MODULE: openzaak.conf.docker
     SECRET_KEY: dev-only-not-for-production
     DB_HOST: oz-db
@@ -104,6 +105,7 @@ envGroups:
   nrc:
     UWSGI_PROCESSES: "1"
     UWSGI_THREADS: "2"
+    CELERY_WORKER_CONCURRENCY: "2"
     DJANGO_SETTINGS_MODULE: nrc.conf.docker
     SECRET_KEY: dev-only-not-for-production
     DB_HOST: nrc-db