1 files changed, 10 insertions, 3 deletions
diff --git a/actionpack/lib/action_view/helpers/form_helper.rb b/actionpack/lib/action_view/helpers/form_helper.rb
index edca950638..a3409ee3c7 100644
--- a/actionpack/lib/action_view/helpers/form_helper.rb
+++ b/actionpack/lib/action_view/helpers/form_helper.rb
@@ -9,6 +9,7 @@ require 'active_support/core_ext/module/method_names'
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/string/output_safety'
 require 'active_support/core_ext/array/extract_options'
+require 'active_support/core_ext/string/inflections'
 
 module ActionView
   # = Action View Form Helpers
@@ -656,15 +657,16 @@ module ActionView
       #     'Accept <a href="/terms">Terms</a>.'.html_safe
       #   end
       def label(object_name, method, content_or_options = nil, options = nil, &block)
+        options ||= {}
+
         content_is_options = content_or_options.is_a?(Hash)
         if content_is_options || block_given?
-          options = content_or_options if content_is_options
+          options.merge!(content_or_options) if content_is_options
           text = nil
         else
           text = content_or_options
         end
 
-        options ||= {}
         InstanceTag.new(object_name, method, self, options.delete(:object)).to_label_tag(text, options, &block)
       end
 
@@ -958,9 +960,14 @@ module ActionView
             object_name = ActiveModel::Naming.param_key(object)
           end
 
-          builder = options[:builder] || ActionView::Base.default_form_builder
+          builder = options[:builder] || default_form_builder
           builder.new(object_name, object, self, options, block)
         end
+
+        def default_form_builder
+          builder = ActionView::Base.default_form_builder
+          builder.respond_to?(:constantize) ? builder.constantize : builder
+        end
     end
 
     class InstanceTag