diff --git a/ext/json/ext/parser/parser.c b/ext/json/ext/parser/parser.c
index c774c791..9a86cd58 100644
--- a/ext/json/ext/parser/parser.c
+++ b/ext/json/ext/parser/parser.c
@@ -2388,6 +2388,7 @@ static VALUE cResumableParser_feed(VALUE self, VALUE str)
 
         if (RB_OBJ_FROZEN_RAW(parser->buffer)) {
             VALUE new_buffer = rb_obj_hide(rb_str_buf_new(remaining + RSTRING_LEN(str)));
+            rb_enc_associate_index(new_buffer, utf8_encindex);
 
             char *old_ptr = RSTRING_PTR(parser->buffer);
             memcpy(RSTRING_PTR(new_buffer), old_ptr + consumed, remaining);
diff --git a/test/json/resumable_parser_test.rb b/test/json/resumable_parser_test.rb
index e93b2314..4cc6c085 100644
--- a/test/json/resumable_parser_test.rb
+++ b/test/json/resumable_parser_test.rb
@@ -205,6 +205,16 @@ def test_rest
     assert_equal '"unterminated string', @parser.rest
   end
 
+  def test_feed_frozen_multibyte_chunks
+    @parser << '{"message":"日本'.freeze
+    refute @parser.parse
+    @parser << '語のつづき"}'.freeze
+    assert @parser.parse
+    value = @parser.value
+    assert_equal({ "message" => "日本語のつづき" }, value)
+    assert_equal Encoding::UTF_8, value["message"].encoding
+  end
+
   def test_eos
     assert_predicate @parser, :eos?