1 files changed, 21 insertions, 0 deletions
diff --git a/test/ruby/test_case.rb b/test/ruby/test_case.rb
index f20d1dfd7e..b9f8ab264d 100644
--- a/test/ruby/test_case.rb
+++ b/test/ruby/test_case.rb
@@ -121,4 +121,25 @@ class TestCase < Test::Unit::TestCase
       end
     }
   end
+
+  module NilEqq
+    refine NilClass do
+      def === other
+        false
+      end
+    end
+  end
+
+  class NilEqqClass
+    using NilEqq
+
+    def eqq(a)
+      case a; when nil then nil; else :not_nil; end
+    end
+  end
+
+
+  def test_deoptimize_nil
+    assert_equal :not_nil, NilEqqClass.new.eqq(nil)
+  end
 end