Spring Boot Prometheus Push Gateway: Metrics missing label

In Spring Boot 3.5.6 I switched to the new recommended Prometheus Pushgateway solution

https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.5-Release-Notes#prometheus-pushgateway

management: prometheus: metrics: export: pushgateway: enabled: ${PROM_PUSH_ENABLED:true} address: ${PROM_PUSH_GATEWAY_ADDRESS:prometheus-pushgateway-cogito-pushgateway.telemetry.svc.cluster.local:9091} scheme: http grouping-key: namespace: ${PROM_PUSH_NAMESPACE_FOR_EXPORT:TBD} shutdown-operation: POST push-rate: ${PROM_PUSH_RATE:5s} job: signal-offload-reconciler format: ${PROM_PUSH_FORMAT:TEXT}

The metrics get pushed to Prometheus (actually Victoria) fine but are missing the label as per the grouping-key (I confirmed that PROM_PUSH_NAMESPACE_FOR_EXPORT is configured on the pod)

Any ideas?