diff --git a/NEWS.md b/NEWS.md
index 4caa78d821..6e2dcc6d24 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -30,6 +30,7 @@ The following default gems are updated.
 
 The following bundled gems are updated.
 
+* minitest 5.21.1
 * net-ftp 0.3.4
 * net-imap 0.4.9.1
 * net-smtp 0.4.0.1
diff --git a/gems/bundled_gems b/gems/bundled_gems
index caa0469c54..22a52318f3 100644
--- a/gems/bundled_gems
+++ b/gems/bundled_gems
@@ -5,7 +5,7 @@
 # - repository-url: URL from where clone for test
 # - revision: revision in repository-url to test
 #   if `revision` is not given, "v"+`version` or `version` will be used.
-minitest        5.20.0  https://github.com/minitest/minitest
+minitest        5.21.1  https://github.com/minitest/minitest
 power_assert    2.0.3   https://github.com/ruby/power_assert
 rake            13.1.0  https://github.com/ruby/rake
 test-unit       3.6.1   https://github.com/test-unit/test-unit