diff --git a/template.rb b/template.rb
index e2c6e224..eda21fbe 100644
--- a/template.rb
+++ b/template.rb
@@ -381,4 +381,12 @@ def create_initial_migration
   run_with_clean_bundler_env "bin/rake db:migrate"
 end
 
+def gsub_file!(path, flag, *args, &block)
+  content = File.binread(path)
+
+  gsub_file(path, flag, *args, &block)
+
+  raise StandardError, "the contents of #{path} did not change!" if content == File.binread(path)
+end
+
 apply_template!
diff --git a/variants/backend-base/app/template.rb b/variants/backend-base/app/template.rb
index 4a045ff3..0ed045dd 100644
--- a/variants/backend-base/app/template.rb
+++ b/variants/backend-base/app/template.rb
@@ -17,6 +17,6 @@
 empty_directory_with_keep_file "app/services"
 
 # Configure the default mailer to use the our default from address
-gsub_file "app/mailers/application_mailer.rb",
-          "default from: 'from@example.com'",
-          "default from: Rails.application.config.app.mail_from"
+gsub_file! "app/mailers/application_mailer.rb",
+           /default from: ['"]from@example\.com['"]/,
+           "default from: Rails.application.config.app.mail_from"
diff --git a/variants/backend-base/config/application.rb b/variants/backend-base/config/application.rb
index b99bf6b9..b4eabfd4 100644
--- a/variants/backend-base/config/application.rb
+++ b/variants/backend-base/config/application.rb
@@ -1,6 +1,6 @@
-gsub_file "config/application.rb",
-          "# config.time_zone = 'Central Time (US & Canada)'",
-          "config.time_zone = 'Wellington'"
+gsub_file! "config/application.rb",
+           /# config.time_zone = ['"]Central Time \(US & Canada\)['"]/,
+           "config.time_zone = 'Wellington'"
 
 insert_into_file "config/application.rb", after: /^require_relative ['"]boot['"]/ do
   # the empty line at the beginning of this string is required
diff --git a/variants/backend-base/config/environments/development.rb b/variants/backend-base/config/environments/development.rb
index d4a52b50..6f0be190 100644
--- a/variants/backend-base/config/environments/development.rb
+++ b/variants/backend-base/config/environments/development.rb
@@ -15,10 +15,6 @@
   RUBY
 end
 
-gsub_file "config/environments/development.rb",
-          "join('tmp', 'caching-dev.txt')",
-          'join("tmp/caching-dev.txt")'
-
-gsub_file "config/environments/development.rb",
-          "config.action_controller.raise_on_missing_callback_actions = true",
-          "# config.action_controller.raise_on_missing_callback_actions = true"
+gsub_file! "config/environments/development.rb",
+           "config.action_controller.raise_on_missing_callback_actions = true",
+           "# config.action_controller.raise_on_missing_callback_actions = true"
diff --git a/variants/backend-base/config/environments/production.rb b/variants/backend-base/config/environments/production.rb
index 52620dd5..eeea4680 100644
--- a/variants/backend-base/config/environments/production.rb
+++ b/variants/backend-base/config/environments/production.rb
@@ -8,14 +8,14 @@
   RUBY
 end
 
-gsub_file "config/environments/production.rb",
-          "# config.force_ssl = true",
-          <<~RUBY
-            ##
-            # `force_ssl` defaults to on. Set `force_ssl` to false if (and only if) RAILS_FORCE_SSL=false, otherwise set it to true.
-            #
-            config.force_ssl = ENV.fetch("RAILS_FORCE_SSL", "true").downcase != "false"
-          RUBY
+gsub_file! "config/environments/production.rb",
+           "config.force_ssl = true",
+           <<~RUBY
+             ##
+             # `force_ssl` defaults to on. Set `force_ssl` to false if (and only if) RAILS_FORCE_SSL=false, otherwise set it to true.
+             #
+             config.force_ssl = ENV.fetch("RAILS_FORCE_SSL", "true").downcase != "false"
+           RUBY
 
 insert_into_file "config/environments/production.rb",
                  after: /# config\.action_mailer\.raise_deliv.*\n/ do
@@ -42,13 +42,13 @@
   RUBY
 end
 
-gsub_file "config/environments/production.rb",
-          "config.log_level = :info",
-          'config.log_level = ENV.fetch("LOG_LEVEL", "info").to_sym'
+gsub_file! "config/environments/production.rb",
+           'ENV.fetch("RAILS_LOG_LEVEL", "info")',
+           'ENV.fetch("RAILS_LOG_LEVEL", ENV.fetch("LOG_LEVEL", "info"))'
 
-gsub_file "config/environments/production.rb",
-          "ActiveSupport::Logger.new(STDOUT)",
-          "ActiveSupport::Logger.new($stdout)"
+gsub_file! "config/environments/production.rb",
+           "ActiveSupport::Logger.new(STDOUT)",
+           "ActiveSupport::Logger.new($stdout)"
 
 insert_into_file "config/environments/production.rb",
                  after: /.*config\.public_file_server\.enabled.*\n/ do
diff --git a/variants/backend-base/config/environments/test.rb b/variants/backend-base/config/environments/test.rb
index 9742ec1c..78442c97 100644
--- a/variants/backend-base/config/environments/test.rb
+++ b/variants/backend-base/config/environments/test.rb
@@ -1,7 +1,3 @@
-gsub_file "config/environments/test.rb",
-          "config.eager_load = false",
-          "config.eager_load = defined?(SimpleCov).present?"
-
 insert_into_file \
   "config/environments/test.rb",
   after: /config\.action_mailer\.delivery_method = :test\n/ do
@@ -17,6 +13,6 @@
   RUBY
 end
 
-gsub_file "config/environments/test.rb",
-          "config.action_controller.raise_on_missing_callback_actions = true",
-          "# config.action_controller.raise_on_missing_callback_actions = true"
+gsub_file! "config/environments/test.rb",
+           "config.action_controller.raise_on_missing_callback_actions = true",
+           "# config.action_controller.raise_on_missing_callback_actions = true"
diff --git a/variants/backend-base/config/template.rb b/variants/backend-base/config/template.rb
index f7b3f880..268333a7 100644
--- a/variants/backend-base/config/template.rb
+++ b/variants/backend-base/config/template.rb
@@ -17,9 +17,9 @@
 copy_file "variants/backend-base/config/initializers/check_env.rb", "config/initializers/check_env.rb"
 copy_file "variants/backend-base/config/initializers/sentry.rb", "config/initializers/sentry.rb"
 
-gsub_file "config/initializers/filter_parameter_logging.rb", /\[:password\]/ do
-  "%w[password secret session cookie csrf]"
-end
+gsub_file! "config/initializers/filter_parameter_logging.rb",
+           / {2}:passw, :secret, /,
+           "  :passw, :secret, :session, :cookie, :csrf, "
 
 apply "variants/backend-base/config/environments/development.rb"
 apply "variants/backend-base/config/environments/production.rb"
@@ -59,7 +59,7 @@
 EO_ROUTES
 
 if File.exist? "config/storage.yml"
-  gsub_file "config/storage.yml", /#   service: S3/ do
+  gsub_file! "config/storage.yml", /#   service: S3/ do
     <<~YAML
       #   service: S3
       #   upload:
diff --git a/variants/deploy_with_ackama_ec2_capistrano/template.rb b/variants/deploy_with_ackama_ec2_capistrano/template.rb
index 0e27dc4e..2186e815 100644
--- a/variants/deploy_with_ackama_ec2_capistrano/template.rb
+++ b/variants/deploy_with_ackama_ec2_capistrano/template.rb
@@ -177,7 +177,7 @@
 
 EO_RUBY
 
-gsub_file("config/deploy.rb", old_generated_cap_config_snippet, new_ackama_cap_config_snippet)
+gsub_file!("config/deploy.rb", old_generated_cap_config_snippet, new_ackama_cap_config_snippet)
 
 insert_into_file "Capfile", after: /install_plugin Capistrano::SCM::Git/ do
   <<~EO_RUBY
diff --git a/variants/deploy_with_capistrano/template.rb b/variants/deploy_with_capistrano/template.rb
index a305f912..62f3a0da 100644
--- a/variants/deploy_with_capistrano/template.rb
+++ b/variants/deploy_with_capistrano/template.rb
@@ -165,7 +165,7 @@
 
 EO_RUBY
 
-gsub_file("config/deploy.rb", old_generated_cap_config_snippet, new_ackama_cap_config_snippet)
+gsub_file!("config/deploy.rb", old_generated_cap_config_snippet, new_ackama_cap_config_snippet)
 
 insert_into_file "Capfile", after: /install_plugin Capistrano::SCM::Git/ do
   <<~EO_RUBY
diff --git a/variants/devise/template.rb b/variants/devise/template.rb
index 8275f549..d0e27339 100644
--- a/variants/devise/template.rb
+++ b/variants/devise/template.rb
@@ -10,29 +10,26 @@
 TERMINAL.puts_header "Generating User model with devise"
 run "bundle exec rails generate devise User"
 
-gsub_file "app/models/user.rb",
-          ":validatable",
-          ":validatable, :lockable"
+gsub_file! "app/models/user.rb",
+           ":validatable",
+           ":validatable, :lockable"
 
 devise_migration_filename = Dir.children("db/migrate").find { |filename| filename.end_with?("_devise_create_users.rb") }
 devise_migration_path = "db/migrate/#{devise_migration_filename}"
 
 TERMINAL.puts_header "Tweaking auto-generated devise migration '#{devise_migration_path}'"
-gsub_file devise_migration_path,
-          "      # t.integer  :failed_attempts",
-          "      t.integer  :failed_attempts"
-gsub_file devise_migration_path,
-          "      # t.string   :unlock_token",
-          "      t.string   :unlock_token"
-gsub_file devise_migration_path,
-          "      # t.datetime :locked_at",
-          "      t.datetime :locked_at"
-gsub_file devise_migration_path,
-          "      # add_index :users, :unlock_token",
-          "      add_index :users, :unlock_token"
-gsub_file devise_migration_path,
-          /  # add_index :users, :unlock_token.+/,
-          "  add_index :users, :unlock_token, unique: true"
+gsub_file! devise_migration_path,
+           "      # t.integer  :failed_attempts",
+           "      t.integer  :failed_attempts"
+gsub_file! devise_migration_path,
+           "      # t.string   :unlock_token",
+           "      t.string   :unlock_token"
+gsub_file! devise_migration_path,
+           "      # t.datetime :locked_at",
+           "      t.datetime :locked_at"
+gsub_file! devise_migration_path,
+           "    # add_index :users, :unlock_token",
+           "    add_index :users, :unlock_token"
 
 TERMINAL.puts_header "Running db migration"
 run "bundle exec rails db:migrate"
@@ -45,51 +42,51 @@
 #
 TERMINAL.puts_header "Tweaking config/initializers/devise.rb"
 
-gsub_file "config/initializers/devise.rb",
-          "  config.mailer_sender = 'please-change-me-at-config-initializers-devise@example.com'",
-          "  config.mailer_sender = Rails.application.config.app.mail_from"
+gsub_file! "config/initializers/devise.rb",
+           "  config.mailer_sender = 'please-change-me-at-config-initializers-devise@example.com'",
+           "  config.mailer_sender = Rails.application.config.app.mail_from"
 
-gsub_file "config/initializers/devise.rb",
-          "  # config.scoped_views = false",
-          "  config.scoped_views = true"
+gsub_file! "config/initializers/devise.rb",
+           "  # config.scoped_views = false",
+           "  config.scoped_views = true"
 
-gsub_file "config/initializers/devise.rb",
-          "  config.password_length = 6..128",
-          "  config.password_length = 16..128"
+gsub_file! "config/initializers/devise.rb",
+           "  config.password_length = 6..128",
+           "  config.password_length = 16..128"
 
-gsub_file "config/initializers/devise.rb",
-          "  # config.paranoid = true",
-          "  config.paranoid = true"
+gsub_file! "config/initializers/devise.rb",
+           "  # config.paranoid = true",
+           "  config.paranoid = true"
 
-gsub_file "config/initializers/devise.rb",
-          /  # config.secret_key = '.+'/,
-          "  # config.secret_key = 'do_not_put_secrets_in_source_control_please'"
+gsub_file! "config/initializers/devise.rb",
+           /  # config.secret_key = '.+'/,
+           "  # config.secret_key = 'do_not_put_secrets_in_source_control_please'"
 
-gsub_file "config/initializers/devise.rb",
-          /  # config.lock_strategy = .+/,
-          "  config.lock_strategy = :failed_attempts"
+gsub_file! "config/initializers/devise.rb",
+           /  # config.lock_strategy = .+/,
+           "  config.lock_strategy = :failed_attempts"
 
-gsub_file "config/initializers/devise.rb",
-          /  # config.unlock_strategy = .+/,
-          "  config.unlock_strategy = :email"
+gsub_file! "config/initializers/devise.rb",
+           /  # config.unlock_strategy = .+/,
+           "  config.unlock_strategy = :email"
 
-gsub_file "config/initializers/devise.rb",
-          "  # config.parent_mailer = 'ActionMailer::Base'",
-          "  config.parent_mailer = 'ApplicationMailer'"
+gsub_file! "config/initializers/devise.rb",
+           "  # config.parent_mailer = 'ActionMailer::Base'",
+           "  config.parent_mailer = 'ApplicationMailer'"
 
-gsub_file "config/initializers/devise.rb",
-          /  # config.maximum_attempts = .+/,
-          <<-EO_CHUNK
+gsub_file! "config/initializers/devise.rb",
+           /  # config.maximum_attempts = .+/,
+           <<-EO_CHUNK
   #
   # https://www.nzism.gcsb.govt.nz/ism-document/#1887 recommends 3 as a default. FYI to
   # be fully compliant with https://www.nzism.gcsb.govt.nz/ism-document/#1887 then only
   # Administrators should be able to unlock.
   config.maximum_attempts = 3
-          EO_CHUNK
+           EO_CHUNK
 
-gsub_file "config/initializers/devise.rb",
-          /  # config.last_attempt_warning = .+/,
-          "  config.last_attempt_warning = true"
+gsub_file! "config/initializers/devise.rb",
+           /  # config.last_attempt_warning = .+/,
+           "  config.last_attempt_warning = true"
 
 ##
 # Add a block to config/routes.rb demonstrating how to create authenticated
@@ -140,13 +137,13 @@
 
 copy_file "app/controllers/users/sessions_controller.rb"
 
-gsub_file "config/routes.rb",
-          "devise_for :users",
-          <<~EO_DEVISE
-            devise_for :users, controllers: {
-              sessions: "users/sessions"
-            }
-          EO_DEVISE
+gsub_file! "config/routes.rb",
+           "devise_for :users",
+           <<~EO_DEVISE
+             devise_for :users, controllers: {
+               sessions: "users/sessions"
+             }
+           EO_DEVISE
 
 insert_into_file "app/models/user.rb", before: /^end/ do
   <<~'RUBY'
@@ -202,14 +199,14 @@ def authenticatable_salt
 copy_file "spec/requests/session_cookie_expiry_spec.rb"
 
 # tell pundit not to check that authorization was called on devise controllers
-gsub_file("app/controllers/application_controller.rb",
-          "after_action :verify_authorized, except: :index",
-          "after_action :verify_authorized, except: :index, unless: :devise_controller?"
-         )
-gsub_file("app/controllers/application_controller.rb",
-          "after_action :verify_policy_scoped, only: :index",
-          "after_action :verify_policy_scoped, only: :index, unless: :devise_controller?"
-         )
+gsub_file!("app/controllers/application_controller.rb",
+           "after_action :verify_authorized, except: :index",
+           "after_action :verify_authorized, except: :index, unless: :devise_controller?"
+          )
+gsub_file!("app/controllers/application_controller.rb",
+           "after_action :verify_policy_scoped, only: :index",
+           "after_action :verify_policy_scoped, only: :index, unless: :devise_controller?"
+          )
 
 TERMINAL.puts_header "Running rubocop -A to fix formatting in files generated by devise"
 run "bundle exec rubocop -A -c ./.rubocop.yml"
diff --git a/variants/frontend-base-typescript/template.rb b/variants/frontend-base-typescript/template.rb
index 25c5a889..93f93330 100644
--- a/variants/frontend-base-typescript/template.rb
+++ b/variants/frontend-base-typescript/template.rb
@@ -35,7 +35,7 @@ def rename_js_file_to_ts(file)
 copy_file ".eslintrc.js", force: true
 copy_file "types.d.ts", force: true
 
-gsub_file(
+gsub_file!(
   "app/frontend/packs/application.ts",
   "process.env.SENTRY_ENV || process.env.RAILS_ENV",
   "process.env.SENTRY_ENV ?? process.env.RAILS_ENV"
@@ -53,7 +53,7 @@ def rename_js_file_to_ts(file)
     return String(images(name));
   };
 EO_TS_ENABLE_IMAGES
-gsub_file("app/frontend/packs/application.ts", js_load_images_chunk, ts_load_images_chunk, force: true)
+gsub_file!("app/frontend/packs/application.ts", js_load_images_chunk, ts_load_images_chunk, force: true)
 
 update_package_json do |package_json|
   package_json["scripts"]["typecheck"] = "tsc -p . --noEmit"
diff --git a/variants/frontend-base/sentry/template.rb b/variants/frontend-base/sentry/template.rb
index 0ee183f6..a0505bb0 100644
--- a/variants/frontend-base/sentry/template.rb
+++ b/variants/frontend-base/sentry/template.rb
@@ -46,7 +46,3 @@
     //
   EO_JS
 end
-
-gsub_file "config/initializers/content_security_policy.rb",
-          /# policy.report_uri ".+"/,
-          'policy.report_uri(ENV["SENTRY_CSP_HEADER_REPORT_ENDPOINT"]) if ENV["SENTRY_CSP_HEADER_REPORT_ENDPOINT"]'
diff --git a/variants/frontend-base/template.rb b/variants/frontend-base/template.rb
index 4ce555ed..cd01e3f4 100644
--- a/variants/frontend-base/template.rb
+++ b/variants/frontend-base/template.rb
@@ -23,19 +23,18 @@
 
 # this is added by shakapacker:install, but we've already got one (with some extra tags)
 # in our template, so remove theirs otherwise the app will error when rendering this
-gsub_file "app/views/layouts/application.html.erb",
-          "    <%= javascript_pack_tag \"application\" %>\n",
-          ""
+gsub_file! "app/views/layouts/application.html.erb",
+           "    <%= javascript_pack_tag \"application\" %>\n",
+           ""
 
 # Configure app/frontend
 
 run "mv app/javascript app/frontend"
 copy_file "config/webpack/webpack.config.js", force: true
 
-gsub_file "config/shakapacker.yml", "source_entry_path: /", "source_entry_path: packs", force: true
-gsub_file "config/shakapacker.yml", "cache_path: tmp/shakapacker", "cache_path: tmp/cache/shakapacker", force: true
-gsub_file "config/shakapacker.yml", "source_path: app/javascript", "source_path: app/frontend", force: true
-gsub_file "config/shakapacker.yml", "ensure_consistent_versioning: false", "ensure_consistent_versioning: true", force: true
+gsub_file! "config/shakapacker.yml", "cache_path: tmp/shakapacker", "cache_path: tmp/cache/shakapacker"
+gsub_file! "config/shakapacker.yml", "source_path: app/javascript", "source_path: app/frontend"
+gsub_file! "config/shakapacker.yml", "ensure_consistent_versioning: false", "ensure_consistent_versioning: true"
 
 old_shakapacker_test_compile_snippet = <<~EO_OLD
   test:
@@ -50,7 +49,7 @@
     # Shakapacker to automatically compile in the test env
     compile: false
 EO_NEW
-gsub_file("config/shakapacker.yml", old_shakapacker_test_compile_snippet, new_shakapacker_test_compile_snippet, force: true)
+gsub_file!("config/shakapacker.yml", old_shakapacker_test_compile_snippet, new_shakapacker_test_compile_snippet, force: true)
 
 empty_directory_with_keep_file "app/frontend/images"
 copy_file "app/frontend/stylesheets/_elements.scss"
@@ -74,13 +73,13 @@
   const imagePath = name => images(name, true);
 EO_ENABLE_IMAGES
 
-gsub_file "app/frontend/packs/application.js", images_disabled_chunk, images_enabled_chunk, force: true
+gsub_file! "app/frontend/packs/application.js", images_disabled_chunk, images_enabled_chunk, force: true
 
 # Configure app/views
-gsub_file "app/views/layouts/application.html.erb",
-          "<%= stylesheet_link_tag(",
-          "<%= stylesheet_pack_tag(",
-          force: true
+gsub_file! "app/views/layouts/application.html.erb",
+           "<%= stylesheet_link_tag(",
+           "<%= stylesheet_pack_tag(",
+           force: true
 
 copy_file "app/frontend/images/example.png"
 body_open_tag_with_img_example = <<~EO_IMG_EXAMPLE
@@ -91,7 +90,7 @@
       %>
       <%= image_pack_tag "images/example.png", alt: "Example Image" %>
 EO_IMG_EXAMPLE
-gsub_file "app/views/layouts/application.html.erb", "<body>", body_open_tag_with_img_example, force: true
+gsub_file! "app/views/layouts/application.html.erb", "<body>", body_open_tag_with_img_example, force: true
 
 # shakapacker will automatically configure webpack to use these so long as the dependencies are present
 yarn_add_dependencies %w[
diff --git a/variants/frontend-bootstrap/template.rb b/variants/frontend-bootstrap/template.rb
index a5cb6805..a285f59a 100644
--- a/variants/frontend-bootstrap/template.rb
+++ b/variants/frontend-bootstrap/template.rb
@@ -13,4 +13,4 @@
   EO_CONTENT
 end
 
-gsub_file "config/initializers/content_security_policy.rb", "policy.img_src     :self", "  policy.img_src     :data, :self", force: true
+gsub_file! "config/initializers/content_security_policy.rb", "policy.img_src     :self", "  policy.img_src     :data, :self", force: true
diff --git a/variants/frontend-react-typescript/template.rb b/variants/frontend-react-typescript/template.rb
index 1a891c81..16382f4b 100644
--- a/variants/frontend-react-typescript/template.rb
+++ b/variants/frontend-react-typescript/template.rb
@@ -15,9 +15,9 @@
 # example files
 remove_file "app/frontend/components/HelloWorld.jsx", force: true
 copy_file "app/frontend/components/HelloWorld.tsx", force: true
-gsub_file(
+gsub_file!(
   "app/views/home/index.html.erb",
-  'react_component("HelloWorld", { greeting: "Hello from react-rails." })',
+  'react_component("HelloWorld", { initialGreeting: "Hello from react-rails." })',
   'react_component("home/index")'
 )
 
diff --git a/variants/frontend-react/template.rb b/variants/frontend-react/template.rb
index 0edf5d4b..bf4f5bc1 100644
--- a/variants/frontend-react/template.rb
+++ b/variants/frontend-react/template.rb
@@ -11,9 +11,9 @@
 # and so should be favored when importing as it is the more specific package
 run "yarn remove @testing-library/dom"
 
-gsub_file "app/frontend/test/stimulus/controllers/add_class_controller.test.js",
-          "'@testing-library/dom'",
-          "'@testing-library/react'"
+gsub_file! "app/frontend/test/stimulus/controllers/add_class_controller.test.js",
+           "'@testing-library/dom'",
+           "'@testing-library/react'"
 
 yarn_add_dependencies %w[
   @babel/preset-react
@@ -40,13 +40,13 @@
   ReactRailsUJS.useContext(componentRequireContext);
 REPLACEMENT
 
-gsub_file "app/frontend/packs/application.js",
-          "ReactRailsUJS.useContext(componentRequireContext);", react_rails_replacement
+gsub_file! "app/frontend/packs/application.js",
+           "ReactRailsUJS.useContext(componentRequireContext);", react_rails_replacement
 
-gsub_file "app/frontend/packs/server_rendering.js",
-          "ReactRailsUJS.useContext(componentRequireContext);", react_rails_replacement
+gsub_file! "app/frontend/packs/server_rendering.js",
+           "ReactRailsUJS.useContext(componentRequireContext);", react_rails_replacement
 
-gsub_file(
+gsub_file!(
   "app/frontend/packs/application.js",
   'var ReactRailsUJS = require("react_ujs")',
   ""
@@ -55,7 +55,7 @@
 prepend_to_file "app/frontend/packs/application.js",
                 "import ReactRailsUJS from 'react_ujs';\n"
 
-gsub_file(
+gsub_file!(
   "app/frontend/packs/server_rendering.js",
   'var ReactRailsUJS = require("react_ujs")',
   "import ReactRailsUJS from 'react_ujs';"
@@ -64,10 +64,6 @@
 # var ReactRailsUJS = require('react_ujs');
 # import ReactRailsUJS from 'react_ujs';
 
-gsub_file "app/views/layouts/application.html.erb",
-          "    <%= javascript_pack_tag \"application\", \"data-turbolinks-track\": \"reload\", defer: true %>\n",
-          "    <%= javascript_pack_tag \"application\" %>\n"
-
 copy_file "jest.config.js"
 
 # example file
diff --git a/variants/sidekiq/template.rb b/variants/sidekiq/template.rb
index fb1e84fc..952b5413 100644
--- a/variants/sidekiq/template.rb
+++ b/variants/sidekiq/template.rb
@@ -62,4 +62,4 @@
   OkComputer::Registry.register "sidekiq_mailers", OkComputer::SidekiqLatencyCheck.new(:mailers)
 EO_NEW
 
-gsub_file("config/initializers/health_checks.rb", original_health_check_chunk, new_health_checks_chunk, force: true)
+gsub_file!("config/initializers/health_checks.rb", original_health_check_chunk, new_health_checks_chunk, force: true)