1 files changed, 5 insertions, 0 deletions
diff --git a/test/ruby/test_hash.rb b/test/ruby/test_hash.rb
index e75cdfe7f9..7b8cf1c6c4 100644
--- a/test/ruby/test_hash.rb
+++ b/test/ruby/test_hash.rb
@@ -2355,6 +2355,11 @@ class TestHashOnly < Test::Unit::TestCase
     end
   end
 
+  def test_bug_21357
+    h = {x: []}.merge(x: nil) { |_k, v1, _v2| v1 }
+    assert_equal({x: []}, h)
+  end
+
   def test_any_hash_fixable
     20.times do
       assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")