diff --git a/Gemfile b/Gemfile
index 20d3630aa2..d454349385 100644
--- a/Gemfile
+++ b/Gemfile
@@ -24,6 +24,7 @@ gem 'jbuilder'
 gem 'jsbundling-rails', '>= 1.2.2'
 gem 'jwt'
 gem 'mini_magick', '>= 4.9.5'
+gem 'mutex_m', '~> 0.3.0'
 gem 'nkf', '~> 0.2.0'
 gem 'omniauth', '~> 2.1.2'
 gem 'omniauth_openid_connect', '>= 0.6.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index b5b83118e8..1469a022df 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -264,6 +264,7 @@ GEM
     minitest (5.25.1)
     msgpack (1.6.0)
     multi_json (1.15.0)
+    mutex_m (0.3.0)
     net-http (0.4.1)
       uri
     net-imap (0.4.17)
@@ -530,6 +531,7 @@ DEPENDENCIES
   jwt
   lograge (~> 0.14.0)
   mini_magick (>= 4.9.5)
+  mutex_m (~> 0.3.0)
   nkf (~> 0.2.0)
   omniauth (~> 2.1.2)
   omniauth-rails_csrf_protection (~> 1.0.2)