diff --git a/lib/haml.rb b/lib/haml.rb
index 2cd78e5d..0fb995e4 100644
--- a/lib/haml.rb
+++ b/lib/haml.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'haml/version'
 
 # The module that contains everything Haml-related:
diff --git a/lib/haml/attribute_compiler.rb b/lib/haml/attribute_compiler.rb
index 347011b3..248280ca 100644
--- a/lib/haml/attribute_compiler.rb
+++ b/lib/haml/attribute_compiler.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'haml/attribute_parser'
 
 module Haml
diff --git a/lib/haml/attribute_parser.rb b/lib/haml/attribute_parser.rb
index 1373b9da..3a89ca45 100644
--- a/lib/haml/attribute_parser.rb
+++ b/lib/haml/attribute_parser.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 begin
   require 'ripper'
 rescue LoadError
diff --git a/lib/haml/buffer.rb b/lib/haml/buffer.rb
index 8ee4b6b0..beb0d471 100644
--- a/lib/haml/buffer.rb
+++ b/lib/haml/buffer.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   # This class is used only internally. It holds the buffer of HTML that
   # is eventually output as the resulting document.
diff --git a/lib/haml/compiler.rb b/lib/haml/compiler.rb
index 0b5f5595..97edc0d1 100644
--- a/lib/haml/compiler.rb
+++ b/lib/haml/compiler.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require 'haml/attribute_builder'
 require 'haml/attribute_compiler'
 require 'haml/temple_line_counter'
diff --git a/lib/haml/engine.rb b/lib/haml/engine.rb
index 547bcd57..953dd0e2 100644
--- a/lib/haml/engine.rb
+++ b/lib/haml/engine.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require 'forwardable'
 
 require 'haml/parser'
diff --git a/lib/haml/error.rb b/lib/haml/error.rb
index d614e4a9..95b3ca67 100644
--- a/lib/haml/error.rb
+++ b/lib/haml/error.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   # An exception raised by Haml code.
   class Error < StandardError
diff --git a/lib/haml/escapable.rb b/lib/haml/escapable.rb
index 18a3c72d..08db5f47 100644
--- a/lib/haml/escapable.rb
+++ b/lib/haml/escapable.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   # Like Temple::Filters::Escapable, but with support for escaping by
   # Haml::Herlpers.html_escape and Haml::Herlpers.escape_once.
diff --git a/lib/haml/exec.rb b/lib/haml/exec.rb
index a29f1fdb..82657f68 100644
--- a/lib/haml/exec.rb
+++ b/lib/haml/exec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'optparse'
 require 'rbconfig'
 require 'pp'
diff --git a/lib/haml/filters.rb b/lib/haml/filters.rb
index f065af4e..7ee72ee8 100644
--- a/lib/haml/filters.rb
+++ b/lib/haml/filters.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require "tilt"
 
 module Haml
diff --git a/lib/haml/generator.rb b/lib/haml/generator.rb
index 4bd9d1e0..19df4a21 100644
--- a/lib/haml/generator.rb
+++ b/lib/haml/generator.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   # Ruby code generator, which is a limited version of Temple::Generator.
   # Limit methods since Haml doesn't need most of them.
diff --git a/lib/haml/helpers.rb b/lib/haml/helpers.rb
index 8ced0db6..df837b60 100644
--- a/lib/haml/helpers.rb
+++ b/lib/haml/helpers.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require 'erb'
 
 module Haml
diff --git a/lib/haml/helpers/action_view_extensions.rb b/lib/haml/helpers/action_view_extensions.rb
index fa82c710..a1c50a43 100644
--- a/lib/haml/helpers/action_view_extensions.rb
+++ b/lib/haml/helpers/action_view_extensions.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   module Helpers
     @@action_view_defined = true
diff --git a/lib/haml/helpers/action_view_mods.rb b/lib/haml/helpers/action_view_mods.rb
index 0330c505..82a83b4b 100644
--- a/lib/haml/helpers/action_view_mods.rb
+++ b/lib/haml/helpers/action_view_mods.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   module Helpers
     module ActionViewMods
diff --git a/lib/haml/helpers/action_view_xss_mods.rb b/lib/haml/helpers/action_view_xss_mods.rb
index 33d69f60..f18199d0 100644
--- a/lib/haml/helpers/action_view_xss_mods.rb
+++ b/lib/haml/helpers/action_view_xss_mods.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module ActionView
   module Helpers
     module CaptureHelper
diff --git a/lib/haml/helpers/safe_erubi_template.rb b/lib/haml/helpers/safe_erubi_template.rb
index 4a315d91..b58b2be0 100644
--- a/lib/haml/helpers/safe_erubi_template.rb
+++ b/lib/haml/helpers/safe_erubi_template.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'action_view'
 
 module Haml
diff --git a/lib/haml/helpers/safe_erubis_template.rb b/lib/haml/helpers/safe_erubis_template.rb
index 4e044086..df3025af 100644
--- a/lib/haml/helpers/safe_erubis_template.rb
+++ b/lib/haml/helpers/safe_erubis_template.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'action_view'
 
 module Haml
@@ -28,4 +29,4 @@ module Haml
       [super, '@output_buffer.to_s'].join("\n")
     end
   end
-end
\ No newline at end of file
+end
diff --git a/lib/haml/helpers/xss_mods.rb b/lib/haml/helpers/xss_mods.rb
index da075d95..0af7cd54 100644
--- a/lib/haml/helpers/xss_mods.rb
+++ b/lib/haml/helpers/xss_mods.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   module Helpers
     # This module overrides Haml helpers to work properly
diff --git a/lib/haml/options.rb b/lib/haml/options.rb
index e2f66206..854807b4 100644
--- a/lib/haml/options.rb
+++ b/lib/haml/options.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   # This class encapsulates all of the configuration options that Haml
   # understands. Please see the {file:REFERENCE.md#options Haml Reference} to
diff --git a/lib/haml/parser.rb b/lib/haml/parser.rb
index 035e7117..939ca2d2 100644
--- a/lib/haml/parser.rb
+++ b/lib/haml/parser.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require 'strscan'
 
 module Haml
diff --git a/lib/haml/plugin.rb b/lib/haml/plugin.rb
index 74e869a7..81e47706 100644
--- a/lib/haml/plugin.rb
+++ b/lib/haml/plugin.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
 
   # This module makes Haml work with Rails using the template handler API.
diff --git a/lib/haml/railtie.rb b/lib/haml/railtie.rb
index b12a1a4c..1a044e19 100644
--- a/lib/haml/railtie.rb
+++ b/lib/haml/railtie.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'haml/template/options'
 
 # check for a compatible Rails version when Haml is loaded
diff --git a/lib/haml/sass_rails_filter.rb b/lib/haml/sass_rails_filter.rb
index ca3bc990..26847804 100644
--- a/lib/haml/sass_rails_filter.rb
+++ b/lib/haml/sass_rails_filter.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   module Filters
     # This is an extension of Sass::Rails's SassTemplate class that allows
diff --git a/lib/haml/template.rb b/lib/haml/template.rb
index 4189be32..34740c48 100644
--- a/lib/haml/template.rb
+++ b/lib/haml/template.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 require 'haml/template/options'
 if defined?(ActiveSupport)
   ActiveSupport.on_load(:action_view) do
diff --git a/lib/haml/template/options.rb b/lib/haml/template/options.rb
index 87782501..546657d6 100644
--- a/lib/haml/template/options.rb
+++ b/lib/haml/template/options.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 # We keep options in its own self-contained file
 # so that we can load it independently in Rails 3,
 # where the full template stuff is lazy-loaded.
diff --git a/lib/haml/temple_engine.rb b/lib/haml/temple_engine.rb
index 34c07835..9c7bee03 100644
--- a/lib/haml/temple_engine.rb
+++ b/lib/haml/temple_engine.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require 'temple'
 require 'haml/escapable'
 require 'haml/generator'
diff --git a/lib/haml/temple_line_counter.rb b/lib/haml/temple_line_counter.rb
index a4cd13fd..41d14540 100644
--- a/lib/haml/temple_line_counter.rb
+++ b/lib/haml/temple_line_counter.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   # A module to count lines of expected code. This would be faster than actual code generation
   # and counting newlines in it.
diff --git a/lib/haml/util.rb b/lib/haml/util.rb
index a1b2d100..3098c967 100644
--- a/lib/haml/util.rb
+++ b/lib/haml/util.rb
@@ -1,4 +1,4 @@
-# encoding: utf-8
+# frozen_string_literal: false
 
 begin
   require 'erubis/tiny'
diff --git a/lib/haml/version.rb b/lib/haml/version.rb
index f7db8009..736808ef 100644
--- a/lib/haml/version.rb
+++ b/lib/haml/version.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 module Haml
   VERSION = "5.0.0.beta.2"
 end