diff --git a/test/gemfiles/rails-6.1.gemfile b/test/gemfiles/rails-6.1.gemfile
index 53669da..2c5f86d 100644
--- a/test/gemfiles/rails-6.1.gemfile
+++ b/test/gemfiles/rails-6.1.gemfile
@@ -1,3 +1,4 @@
 source "https://rubygems.org"
 gemspec path: "../.."
 gem "activerecord", "~> 6.1.0"
+gem "mutex_m"
diff --git a/test/gemfiles/rails-7.0.gemfile b/test/gemfiles/rails-7.0.gemfile
index aa81086..67bb5b4 100644
--- a/test/gemfiles/rails-7.0.gemfile
+++ b/test/gemfiles/rails-7.0.gemfile
@@ -1,3 +1,4 @@
 source "https://rubygems.org"
 gemspec path: "../.."
 gem "activerecord", "~> 7.0.0"
+gem "mutex_m"