diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 5e869ad..10aa281 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Copyright (C) 2024 Manuel Bustillo
 
 module ApplicationHelper
diff --git a/app/helpers/expenses_helper.rb b/app/helpers/expenses_helper.rb
index af8a78e..2806ac9 100644
--- a/app/helpers/expenses_helper.rb
+++ b/app/helpers/expenses_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Copyright (C) 2024 Manuel Bustillo
 
 module ExpensesHelper
diff --git a/app/helpers/groups_helper.rb b/app/helpers/groups_helper.rb
index 311c1a2..aa6ffcc 100644
--- a/app/helpers/groups_helper.rb
+++ b/app/helpers/groups_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Copyright (C) 2024 Manuel Bustillo
 
 module GroupsHelper
diff --git a/app/helpers/guests_helper.rb b/app/helpers/guests_helper.rb
index ca740f6..d381a71 100644
--- a/app/helpers/guests_helper.rb
+++ b/app/helpers/guests_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Copyright (C) 2024 Manuel Bustillo
 
 module GuestsHelper
diff --git a/app/helpers/tables_arrangements_helper.rb b/app/helpers/tables_arrangements_helper.rb
index 637e079..1ec0aab 100644
--- a/app/helpers/tables_arrangements_helper.rb
+++ b/app/helpers/tables_arrangements_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Copyright (C) 2024 Manuel Bustillo
 
 module TablesArrangementsHelper