How to scale the ingress `router` pod in OpenShift 4

Issue

• Is it possible to change the number of replicas of the ingress router pod?

• It is not working when editing the deployment/replicaset resources directly.

  $ oc edit deployment/router-default -n openshift-ingress
  <--snip-->
  spec:
    replicas: 2  -->  change to 3
  
  $ oc get -o yaml deployment/router-default -n openshift-ingress | grep replicas
    replicas: 2
  

  $ oc edit replicaset/router-default-587f757749 -n openshift-ingress
  <--snip-->
  spec:
    replicas: 2  -->  change to 3
  
  $ oc get -o yaml replicaset/router-default-587f757749 -n openshift-ingress | grep replicas
    replicas: 2