diff --git a/lib/logstash/filters/sleep.rb b/lib/logstash/filters/sleep.rb
index ce70576b9..a936f79ab 100644
--- a/lib/logstash/filters/sleep.rb
+++ b/lib/logstash/filters/sleep.rb
@@ -88,7 +88,7 @@ class LogStash::Filters::Sleep < LogStash::Filters::Base
     end
 
     if @replay
-      clock = event.ruby_timestamp.to_f
+      clock = event["@timestamp"].to_f
       if @last_clock
         delay = clock - @last_clock
         time = delay/time