diff --git a/lib/krane/kubernetes_resource/stateful_set.rb b/lib/krane/kubernetes_resource/stateful_set.rb
index ff579e768..4f06d7029 100644
--- a/lib/krane/kubernetes_resource/stateful_set.rb
+++ b/lib/krane/kubernetes_resource/stateful_set.rb
@@ -3,6 +3,7 @@
 module Krane
   class StatefulSet < PodSetBase
     TIMEOUT = 10.minutes
+    ONDELETE = 'OnDelete'
     SYNC_DEPENDENCIES = %w(Pod)
     REQUIRED_ROLLOUT_TYPES = %w(full).freeze
     attr_reader :pods
@@ -30,7 +31,7 @@ def deploy_succeeded?
         success &= desired_replicas == status_data['readyReplicas'].to_i
         success &= desired_replicas == status_data['currentReplicas'].to_i
 
-      elsif update_strategy == 'OnDelete'
+      elsif update_strategy == ONDELETE
         unless @success_assumption_warning_shown
           @logger.warn("WARNING: Your StatefulSet's updateStrategy is set to OnDelete, "\
                        "which means the deployment won't succeed until all pods are updated by deletion.")
@@ -47,7 +48,7 @@ def deploy_succeeded?
     end
 
     def deploy_failed?
-      return false if update_strategy == 'OnDelete' && required_rollout != 'full'
+      return false if update_strategy == ONDELETE && required_rollout != 'full'
       pods.present? && pods.any?(&:deploy_failed?) &&
       observed_generation == current_generation
     end