[TxMt] Ruby > Run = undefined method 'htmlize'

I have recently become unable to run tests in TextMate using the Ruby bundle's Command-R "Run" option. It used to work, but at some point in the past few weeks I started getting this error:

/Library/Application Support/TextMate/Bundles/Ruby.tmbundle/Support/RubyMate/run_script.rb:143: undefined method `htmlize' for main:Object (NoMethodError) from /Library/Application Support/TextMate/Bundles/Ruby.tmbundle/Support/RubyMate/run_script.rb:101

Using TextMate Version 1.5.3 (1258) My /Library/Application Support/TextMate/Bundles directory is a svn checkout of http://macromates.com/svn/Bundles/trunk/Bundles Revision 5277