diff --git a/gemfiles/rails_6.1.gemfile b/gemfiles/rails_6.1.gemfile
index 2b4c9279..a28d35e4 100644
--- a/gemfiles/rails_6.1.gemfile
+++ b/gemfiles/rails_6.1.gemfile
@@ -4,5 +4,6 @@ source 'https://rubygems.org'
 
 gem 'rails', '6.1.3.1'
 gem 'sqlite3'
+gem 'mutex_m'
 
 gemspec :path => '../'
diff --git a/gemfiles/rails_7.gemfile b/gemfiles/rails_7.gemfile
index 170e929d..ae592d0f 100644
--- a/gemfiles/rails_7.gemfile
+++ b/gemfiles/rails_7.gemfile
@@ -4,5 +4,6 @@ source 'https://rubygems.org'
 
 gem 'rails', '~> 7.0.3'
 gem 'sqlite3'
+gem 'mutex_m'
 
 gemspec :path => '../'