diff --git a/lib/nested_form/builder_mixin.rb b/lib/nested_form/builder_mixin.rb
index 26a98877..83727a84 100644
--- a/lib/nested_form/builder_mixin.rb
+++ b/lib/nested_form/builder_mixin.rb
@@ -88,14 +88,15 @@ def fields_for_with_nested_attributes(association_name, *args)
     end
 
     def fields_for_nested_model(name, object, options, block)
-      classes = 'fields'
+      classes = options.fetch(:nested_wrapper_class, '').dup
+      classes << ' fields'
       classes << ' marked_for_destruction' if object.respond_to?(:marked_for_destruction?) && object.marked_for_destruction?
 
       perform_wrap   = options.fetch(:nested_wrapper, true)
       perform_wrap &&= options[:wrapper] != false # wrap even if nil
 
       if perform_wrap
-        @template.content_tag(:div, super, :class => classes)
+        @template.content_tag(:div, super, :class => classes.strip)
       else
         super
       end