[katello-devel] failed travis on 1.8.7, green on 1.9.3

[Tom McKay]

https://travis-ci.org/thomasmckay/katello/builds/5257001

/home/travis/.rvm/gems/ruby-1.8.7-p371/gems/activerecord-3.0.10/lib/active_record/base.rb:1014:in `method_missing': undefined method `use_index_of' for #<Class:0xb41c5f84> (NoMethodError)
  from /home/travis/build/thomasmckay/katello/src/app/models/hypervisor.rb:14

class Hypervisor < System
  use_index_of System      <-- line 14


Any idea why this would be a problem just on 1.8.7?