Issue #8872 has been updated by nagachika (Tomoyuki Chikanaga). How about 2.0.0? Can I change the behavior at 2.0.0 to same with 2.1? If so I'll backport r43913 to fix SEGV. ---------------------------------------- Backport #8872: Case statements do not honor a refinement of the '===' method https://bugs.ruby-lang.org/issues/8872#change-43808 Author: jconley88 (Jon Conley) Status: Assigned Priority: Normal Assignee: matz (Yukihiro Matsumoto) Category: Target version: =begin Below, I've redefined the ((|===|)) method of symbol to always return true. In ((|RefineTest#uses_refinement|)), I call ((|===|)) directly and the refined method is called. In ((|RefineTest#does_not_use_refinement|)), the ((|===|)) method is called indirectly through a case statement. If the refined ((|===|)) method was called, the result should be ((*'The refinement was used'*)), but this code currently returns ((*'The refinement was not used'*)). module RefineSymbol refine Symbol do def ===(other) true end end end using RefineSymbol class RefineTest def uses_refinement :a === :b end def does_not_use_refinement case :a when :b 'The refinement was used' else 'The refinement was not used' end end end rt = RefineTest.new rt.uses_refinement # => true rt.does_not_use_refinement # => expected 'The refinement was used' but got 'The refinement was not used' =end -- http://bugs.ruby-lang.org/