diff --git a/actionview/lib/action_view/helpers/form_tag_helper.rb b/actionview/lib/action_view/helpers/form_tag_helper.rb
index 7d1cdc5a68..ff5d278b85 100644
--- a/actionview/lib/action_view/helpers/form_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/form_tag_helper.rb
@@ -862,7 +862,7 @@ module ActionView
 
         # see http://www.w3.org/TR/html4/types.html#type-name
         def sanitize_to_id(name)
-          name.to_s.delete(']').gsub(/[^-a-zA-Z0-9:.]/, "_")
+          name.to_s.delete(']').tr('^-a-zA-Z0-9:.', "_")
         end
     end
   end
diff --git a/actionview/lib/action_view/template.rb b/actionview/lib/action_view/template.rb
index f398f9bfa3..379f31bdaf 100644
--- a/actionview/lib/action_view/template.rb
+++ b/actionview/lib/action_view/template.rb
@@ -321,7 +321,7 @@ module ActionView
       end
 
       def identifier_method_name #:nodoc:
-        inspect.gsub(/[^a-z_]/, '_')
+        inspect.tr('^a-z_', '_')
       end
 
       def instrument(action, &block)