diff --git a/tests/json_generator_test.rb b/tests/json_generator_test.rb
index fd70b0269..2436fa062 100755
--- a/tests/json_generator_test.rb
+++ b/tests/json_generator_test.rb
@@ -446,6 +446,15 @@ def test_invalid_encoding_string
   end
 
   if defined?(JSON::Ext::Generator) and RUBY_PLATFORM != "java"
+    def test_valid_utf8_in_different_encoding
+      utf8_string = "€™"
+      wrong_encoding_string = utf8_string.b
+      # This behavior is historical. Not necessary desirable. We should deprecated it.
+      # The pure and java version of the gem already don't behave this way.
+      assert_equal utf8_string.to_json, wrong_encoding_string.to_json
+      assert_equal JSON.dump(utf8_string), JSON.dump(wrong_encoding_string)
+    end
+
     def test_string_ext_included_calls_super
       included = false
 
diff --git a/tests/ractor_test.rb b/tests/ractor_test.rb
index ba9bf7a7f..36196ed23 100644
--- a/tests/ractor_test.rb
+++ b/tests/ractor_test.rb
@@ -9,7 +9,7 @@
 
 class JSONInRactorTest < Test::Unit::TestCase
   def test_generate
-    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
+    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}", ignore_stderr: true)
     begin;
       $VERBOSE = nil
       require "json"