diff --git a/lib/logstash/outputs/amqp.rb b/lib/logstash/outputs/amqp.rb
index 595ce1731..dea7e706d 100644
--- a/lib/logstash/outputs/amqp.rb
+++ b/lib/logstash/outputs/amqp.rb
@@ -94,7 +94,7 @@ class LogStash::Outputs::Amqp < LogStash::Outputs::Base
 
   public
   def receive(event)
-    key = event.sprintf(@key)
+    key = event.sprintf(@key) if @key
     @logger.debug(["Sending event", { :destination => to_s, :event => event, :key => key }])
     begin
       if @target