Index: app/helpers/application_helper.rb
===================================================================
--- app/helpers/application_helper.rb	(revision 17151)
+++ app/helpers/application_helper.rb	(working copy)
@@ -1424,6 +1424,7 @@
       if email.present?
         gravatar(email.to_s.downcase, options) rescue nil
       else
+        options[:size] = options[:size].to_s
         image_tag 'anonymous.png',
                   GravatarHelper::DEFAULT_OPTIONS
                     .except(:default, :rating, :ssl).merge(options)