diff --git a/contrib/ruby_event_store-sidekiq_scheduler/lib/ruby_event_store/sidekiq_scheduler.rb b/contrib/ruby_event_store-sidekiq_scheduler/lib/ruby_event_store/sidekiq_scheduler.rb
index 6cef2e7f39..b144346d2e 100644
--- a/contrib/ruby_event_store-sidekiq_scheduler/lib/ruby_event_store/sidekiq_scheduler.rb
+++ b/contrib/ruby_event_store-sidekiq_scheduler/lib/ruby_event_store/sidekiq_scheduler.rb
@@ -7,7 +7,7 @@ def initialize(serializer:)
     end
 
     def call(klass, record)
-      klass.perform_async(record.serialize(serializer).to_h)
+      klass.perform_async(record.serialize(serializer).to_h.transform_keys!(&:to_s))
     end
 
     def verify(subscriber)