diff --git a/spec/fixtures/apps/rails-initializer-config/Gemfile b/spec/fixtures/apps/rails-initializer-config/Gemfile
index be34a963..71c9f678 100644
--- a/spec/fixtures/apps/rails-initializer-config/Gemfile
+++ b/spec/fixtures/apps/rails-initializer-config/Gemfile
@@ -1,8 +1,10 @@
 source 'https://rubygems.org'
 
 ruby_version = Gem::Version.new(RUBY_VERSION.dup)
-
-gem 'mutex_m', '0.3.0' if ruby_version >= Gem::Version.new('3.4')
+if ruby_version >= Gem::Version.new('3.4')
+    gem 'mutex_m', '0.3.0'
+    gem 'base64', '0.2.0'
+end
 
 gem 'railties', ruby_version <= Gem::Version.new('2.6') ? '4.2.10' : '~> 6.0.2', require: %w(action_controller rails)
 gem 'rake', ruby_version <= Gem::Version.new('1.9.3') ? '~> 11.3.0' : '~> 12.3.0'
diff --git a/spec/fixtures/apps/rails-invalid-initializer-config/Gemfile b/spec/fixtures/apps/rails-invalid-initializer-config/Gemfile
index be34a963..ea2524da 100644
--- a/spec/fixtures/apps/rails-invalid-initializer-config/Gemfile
+++ b/spec/fixtures/apps/rails-invalid-initializer-config/Gemfile
@@ -2,7 +2,10 @@ source 'https://rubygems.org'
 
 ruby_version = Gem::Version.new(RUBY_VERSION.dup)
 
-gem 'mutex_m', '0.3.0' if ruby_version >= Gem::Version.new('3.4')
+if ruby_version >= Gem::Version.new('3.4')
+    gem 'mutex_m', '0.3.0'
+    gem 'base64', '0.2.0'
+end
 
 gem 'railties', ruby_version <= Gem::Version.new('2.6') ? '4.2.10' : '~> 6.0.2', require: %w(action_controller rails)
 gem 'rake', ruby_version <= Gem::Version.new('1.9.3') ? '~> 11.3.0' : '~> 12.3.0'
diff --git a/spec/fixtures/apps/rails-no-config/Gemfile b/spec/fixtures/apps/rails-no-config/Gemfile
index be34a963..ea2524da 100644
--- a/spec/fixtures/apps/rails-no-config/Gemfile
+++ b/spec/fixtures/apps/rails-no-config/Gemfile
@@ -2,7 +2,10 @@ source 'https://rubygems.org'
 
 ruby_version = Gem::Version.new(RUBY_VERSION.dup)
 
-gem 'mutex_m', '0.3.0' if ruby_version >= Gem::Version.new('3.4')
+if ruby_version >= Gem::Version.new('3.4')
+    gem 'mutex_m', '0.3.0'
+    gem 'base64', '0.2.0'
+end
 
 gem 'railties', ruby_version <= Gem::Version.new('2.6') ? '4.2.10' : '~> 6.0.2', require: %w(action_controller rails)
 gem 'rake', ruby_version <= Gem::Version.new('1.9.3') ? '~> 11.3.0' : '~> 12.3.0'