On a related note, editing the BridgeSupport file for DictionaryServices also solved my problems when dealing with Boxed objects. The following code (by Craig): framework '/System/Library/Frameworks/CoreServices.framework/Frameworks/DictionaryServices.framework' word = 'History' word_len = DCSGetTermRangeInString(nil, word, 0); res = DCSCopyTextDefinition(nil, word, word_len) puts "Definition for: #{word}" puts res would crash since DCSGetTermRangeInString wouldn't return a proper CFRange. Changing <function name='DCSGetTermRangeInString'> <arg type='^{__DCSDictionary=}'/> <arg type='^{__CFString=}'/> <arg type64='q' type='l'/> <retval type64='{?=qq}' type='{?=ii}'/> </function> to <function name='DCSGetTermRangeInString'> <arg type='^{__DCSDictionary=}'/> <arg type='^{__CFString=}'/> <arg type64='q' type='l'/> <retval type64='{_CFRange=qq}' type='{_CFRange=ii}'/> </function> in /System/Library/Frameworks/CoreServices.framework/Frameworks/DictionaryServices.framework/Resources/BridgeSupport/DictionaryServices.bridgesupport did the trick. Seems like macruby-head doesn't have to deal with these issues though.