diff --git a/test/ruby/test_marshal.rb b/test/ruby/test_marshal.rb
index e4f6e5e91a..2aa2a38f80 100644
--- a/test/ruby/test_marshal.rb
+++ b/test/ruby/test_marshal.rb
@@ -678,7 +678,6 @@ class TestMarshal < Test::Unit::TestCase
 
   def test_recursive_userdef
     t = Time.utc(0)
-    str = "b".b
     t.instance_eval {@v = t}
     assert_raise_with_message(RuntimeError, /recursive\b.*\b_dump/) do
       Marshal.dump(t)