diff --git a/lib/krane/kubernetes_resource/stateful_set.rb b/lib/krane/kubernetes_resource/stateful_set.rb
index 95d40336b..26a8aa9ef 100644
--- a/lib/krane/kubernetes_resource/stateful_set.rb
+++ b/lib/krane/kubernetes_resource/stateful_set.rb
@@ -19,6 +19,9 @@ def status
     end
 
     def deploy_succeeded?
+      success = observed_generation == current_generation &&
+        desired_replicas == status_data['readyReplicas'].to_i &&
+        status_data['currentRevision'] == status_data['updateRevision']
       if update_strategy == ONDELETE
         # Gem cannot monitor update since it doesn't occur until delete
         unless @success_assumption_warning_shown
@@ -27,11 +30,10 @@ def deploy_succeeded?
                        "Consider switching to rollingUpdate.")
           @success_assumption_warning_shown = true
         end
+      else
+        success &= desired_replicas == status_data['currentReplicas'].to_i
       end
-      observed_generation == current_generation &&
-      status_data['currentRevision'] == status_data['updateRevision'] &&
-      desired_replicas == status_data['readyReplicas'].to_i &&
-      desired_replicas == status_data['currentReplicas'].to_i
+      success
     end
 
     def deploy_failed?
diff --git a/lib/krane/restart_task.rb b/lib/krane/restart_task.rb
index 780bcef94..d729ae12b 100644
--- a/lib/krane/restart_task.rb
+++ b/lib/krane/restart_task.rb
@@ -213,7 +213,7 @@ def patch_daemonset_with_restart(record)
     def delete_statefulset_pods(record)
       pods = kubeclient.get_pods(namespace: record.metadata.namespace)
       pods.select! do |pod|
-        pod.metadata.ownerReferences.find { |ref| ref.uid == record.metadata.uid }
+        pod.metadata&.ownerReferences&.find { |ref| ref.uid == record.metadata.uid }
       end
       pods.each { |pod| kubeclient.delete_pod(pod.metadata.name, pod.metadata.namespace) }
     end
diff --git a/test/integration/restart_task_test.rb b/test/integration/restart_task_test.rb
index a6c7a89b2..d13a78193 100644
--- a/test/integration/restart_task_test.rb
+++ b/test/integration/restart_task_test.rb
@@ -36,7 +36,8 @@ def test_restart_by_annotation
   end
 
   def test_restart_statefulset_on_delete_restarts_child_pods
-    result = deploy_fixtures("hello-cloud", subset: "stateful_set.yml") do |fixtures|
+    result = deploy_fixtures("hello-cloud", subset: ["configmap-data.yml", "unmanaged-pod-1.yml.erb",
+      "stateful_set.yml"], render_erb: true) do |fixtures|
       statefulset = fixtures["stateful_set.yml"]["StatefulSet"].first
       statefulset["spec"]["updateStrategy"] = { "type" => "OnDelete" }
     end