Can't parse simple xml

Why is this simple test failing? I really don't understand the error message:

# echo "<data>123</data>" | logstash -e "input { stdin {} } filter { xml { source => "message" } } output { stdout {} }"                                        
Logstash startup completed
Trouble parsing xml with XmlSimple {:source=>"message", :value=>"<data>123</data>", :exception=>#<NoMethodError: undefined method `start_with?' for nil:NilClass>, :backtrace=>["/usr/local/logstash-1.5.4/vendor/bundle/jruby/1.9/gems/logstash-core-1.5.4-java/lib/logstash/event.rb:140:in `[]='", "/usr/local/logstash-1.5.4/vendor/bundle/jruby/1.9/gems/logstash-filter-xml-1.0.0/lib/logstash/filters/xml.rb:129:in `filter'", "/usr/local/logstash-1.5.4/vendor/bundle/jruby/1.9/gems/logstash-core-1.5.4-java/lib/logstash/filters/base.rb:163:in `multi_filter'", "org/jruby/RubyArray.java:1613:in `each'", "/usr/local/logstash-1.5.4/vendor/bundle/jruby/1.9/gems/logstash-core-1.5.4-java/lib/logstash/filters/base.rb:160:in `multi_filter'", "(eval):41:in `filter_func'", "/usr/local/logstash-1.5.4/vendor/bundle/jruby/1.9/gems/logstash-core-1.5.4-java/lib/logstash/pipeline.rb:219:in `filterworker'", "/usr/local/logstash-1.5.4/vendor/bundle/jruby/1.9/gems/logstash-core-1.5.4-java/lib/logstash/pipeline.rb:157:in `start_filters'"], :level=>:warn}
2015-09-12T15:53:57.722Z jman <data>123</data>

You have to set the target parameter. See github.com/elastic/logstash issue #3843 for more on this.