I'm not sure that this is a bug, but at least it is an incompatibility w/ mri and jruby. The issue is that jruby yaml reacts badly to special characters in the yaml file. Try the following (using the attached yaml file) both w/ mri and jruby: D:\ars_magica\ars_magica>ruby -e "require 'yaml';File.open('errorsample.yaml') {|ya| x=YAML.load(ya);puts x['Foo']['desc ription']}" This is something ΓÇô 10. D:\ars_magica\ars_magica>jruby -e "require 'yaml';File.open('errorsample.yaml') {|ya| x=YAML.load(ya);puts x['Foo']['description']}}" ScannerImpl.java:282:in `org.jvyaml.ScannerImpl.checkPrintable': org.jvyaml.YAMLException: At 56 we found: ?. Special ch aracters are not allowed (NativeException) <removed lengthy stack trace> E.g. I have some existing data in yaml that the mri is able to handle just fine, but the app does not work in jruby due to this difference in the yaml implementations. In the very least, the jruby version could tell on what line of the yaml input the problem is on - telling the index of the problematic character from the beginning of the file is not so useful (although not totally useless, either).