diff --git a/activejob/lib/active_job/queue_adapter.rb b/activejob/lib/active_job/queue_adapter.rb
index 298feb8393..ede4d4e269 100644
--- a/activejob/lib/active_job/queue_adapter.rb
+++ b/activejob/lib/active_job/queue_adapter.rb
@@ -10,7 +10,7 @@ module ActiveJob
 
     included do
       class_attribute :_queue_adapter_name, instance_accessor: false, instance_predicate: false
-      class_attribute :_queue_adapter, default: :async, instance_accessor: false, instance_predicate: false
+      class_attribute :_queue_adapter, instance_accessor: false, instance_predicate: false
 
       delegate :queue_adapter, to: :class