diff --git a/config/initializers/10-patches.rb b/config/initializers/10-patches.rb
index e4a110cfa..c2d0a5fad 100644
--- a/config/initializers/10-patches.rb
+++ b/config/initializers/10-patches.rb
@@ -50,6 +50,41 @@ module ActionView
   end
 end
 
+# Do not HTML escape text templates
+module ActionView
+  class Template
+    module Handlers
+      class ERB
+        def call(template)
+          if template.source.encoding_aware?
+            # First, convert to BINARY, so in case the encoding is
+            # wrong, we can still find an encoding tag
+            # (<%# encoding %>) inside the String using a regular
+            # expression
+            template_source = template.source.dup.force_encoding("BINARY")
+
+            erb = template_source.gsub(ENCODING_TAG, '')
+            encoding = $2
+
+            erb.force_encoding valid_encoding(template.source.dup, encoding)
+
+            # Always make sure we return a String in the default_internal
+            erb.encode!
+          else
+            erb = template.source.dup
+          end
+
+          self.class.erb_implementation.new(
+            erb,
+            :trim => (self.class.erb_trim_mode == "-"),
+            :escape => template.identifier =~ /\.text/ # only escape HTML templates
+          ).src
+        end
+      end
+    end
+  end
+end
+
 ActionView::Base.field_error_proc = Proc.new{ |html_tag, instance| html_tag || ''.html_safe }
 
 require 'mail'
diff --git a/test/unit/mailer_test.rb b/test/unit/mailer_test.rb
index 3721ad497..ae755a51a 100644
--- a/test/unit/mailer_test.rb
+++ b/test/unit/mailer_test.rb
@@ -542,10 +542,27 @@ class MailerTest < ActiveSupport::TestCase
     end
   end
 
-private
+  def test_should_escape_html_templates_only
+    Issue.generate!(:project_id => 1, :tracker_id => 1, :subject => 'Subject with a <tag>')
+    mail = last_email
+    assert_equal 2, mail.parts.size
+    assert_include '<tag>', text_part.body.encoded
+    assert_include '&lt;tag&gt;', html_part.body.encoded
+  end
+
+  private
+
   def last_email
     mail = ActionMailer::Base.deliveries.last
     assert_not_nil mail
     mail
   end
+
+  def text_part
+    last_email.parts.detect {|part| part.content_type.include?('text/plain')}
+  end
+
+  def html_part
+    last_email.parts.detect {|part| part.content_type.include?('text/html')}
+  end
 end