diff --git a/test/ruby/test_defined.rb b/test/ruby/test_defined.rb
index 7533e7d9dd..6c63c7fb27 100644
--- a/test/ruby/test_defined.rb
+++ b/test/ruby/test_defined.rb
@@ -1,4 +1,5 @@
 require 'test/unit'
+require_relative 'envutil'
 
 class TestDefined < Test::Unit::TestCase
   class Foo
@@ -204,4 +205,8 @@ class TestDefined < Test::Unit::TestCase
     o.extend(m)
     assert_equal("super", o.x)
   end
+
+  def test_super_toplevel
+    assert_separately([], "assert_nil(defined?(super))")
+  end
 end