On Jun 8, 9:20 ¨Βν¬ Κοθξ ΖενιξεμμΌκο®®®ΐβιτσβυιμδες®γονχςοτεΊ > This is a pretty trivial error to generate. Just reference the > constant that doesn't exist: > > $ irb > ruby-1.9.2-p180 :001 > module X; module Foo; end; end > > nil > ruby-1.9.2-p180 :002 > X::Foo::X > NameError: uninitialized constant X::Foo::X Ah good point. I made an assumption. A qualifier then: X does exist. How about this must be as top of your solution. module X; end