diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index 982933b..2771ff6 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -4376,7 +4376,9 @@ gzreader_charboundary(struct gzfile *gz, rb_len_t n)
     if (l < n) {
 	int n_bytes = rb_enc_precise_mbclen(p, e, gz->enc);
 	if (MBCLEN_NEEDMORE_P(n_bytes)) {
-	    if ((l = gzfile_fill(gz, n + MBCLEN_NEEDMORE_LEN(n_bytes), Qnil)) > 0) {
+	    /* the character needs MBCLEN_NEEDMORE_LEN bytes beyond the END of the
+	     * buffer, which may lie past n */
+	    if ((l = gzfile_fill(gz, ZSTREAM_BUF_FILLED(&gz->z) + MBCLEN_NEEDMORE_LEN(n_bytes), Qnil)) > 0) {
 		return l;
 	    }
 	}
diff --git a/test/zlib/test_zlib.rb b/test/zlib/test_zlib.rb
index 1f9cb81..b932034 100644
--- a/test/zlib/test_zlib.rb
+++ b/test/zlib/test_zlib.rb
@@ -1367,6 +1367,22 @@ def test_reader_wrap
       }
     end
 
+    def test_gets_limit_multibyte_boundary
+      # The inflated buffer ends in the middle of a character whenever a
+      # 2048-byte read of compressed data does; gets(limit) must still return
+      # whole characters (same as IO#gets(limit)).
+      content = (("\u3042\u3044\u3046" * 700) + "\n") * 3
+      [1, 4, 7, 10].each do |limit|
+        r = Zlib::GzipReader.new(StringIO.new(Zlib.gzip(content, level: 0)))
+        lines = []
+        while (line = r.gets(limit))
+          lines << line
+        end
+        assert_equal(content, lines.join)
+        assert_empty(lines.reject(&:valid_encoding?), "limit #{limit}")
+      end
+    end
+
     def test_corrupted_header
       gz = Zlib::GzipWriter.new(StringIO.new(s = "".dup))
       gz.orig_name = "X"