# Solution for "No definition for XXX" gem installation errors

**URL:** <https://www.ruby-forum.com/t/solution-for-no-definition-for-xxx-gem-installation-errors/193295>\
**Category:** Rails\
**Created:** [August 15, 2010, 2:43am UTC](https://www.ruby-forum.com/t/solution-for-no-definition-for-xxx-gem-installation-errors/193295 "2010-08-15T02:43:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![turkan](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e8c25b/32.png) [@turkan](https://www.ruby-forum.com/u/turkan)\
**Post date:** [August 15, 2010, 2:43am UTC](https://www.ruby-forum.com/t/solution-for-no-definition-for-xxx-gem-installation-errors/193295/1 "2010-08-15T02:43:13Z")

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Hello.

I had a problem with RDoc when installing various gems (mysql,  
mongrel). I often got error messages of the kind “No definition for  
XXX”. When doing a google search with that error then it seems that a  
lot of people do have that problem. I never read a solution (most  
recommend to simply suppress the generation of the documentation). But  
a simple “gem install rdoc-data” seems to solve the problem. I don’t  
know why (maybe you can tell me?!), but it works.

Best regards,  
Kai