1 files changed, 12 insertions, 0 deletions
diff --git a/test/ruby/test_keyword.rb b/test/ruby/test_keyword.rb
index 82037575f9..df366845fe 100644
--- a/test/ruby/test_keyword.rb
+++ b/test/ruby/test_keyword.rb
@@ -603,4 +603,16 @@ class TestKeywordArguments < Test::Unit::TestCase
       assert_equal({x: 1, y: 2, **h}, obj.foo)
     }
   end
+
+  def test_non_keyword_hash_subclass
+    bug12884 = '[ruby-core:77813] [Bug #12884]'
+    klass = EnvUtil.labeled_class("Child", Hash)
+    obj = Object.new
+    def obj.t(params = klass.new, d: nil); params; end
+    x = klass.new
+    x["foo"] = "bar"
+    result = obj.t(x)
+    assert_equal(x, result)
+    assert_kind_of(klass, result, bug12884)
+  end
 end