diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 80a8a50d..2ecf9671 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -962,6 +962,7 @@ module ApplicationHelper
     [:default, :size, :rating, :filetype].each {|key| gravatarify_options[key] = options.delete key}
     # Default size is 50x50 px
     gravatarify_options[:size] ||= 50
+    options[:class] ||= 'gravatar'
     gravatarify_options[:html] = options
     gravatar_tag email, gravatarify_options
   end
diff --git a/test/unit/helpers/application_helper_test.rb b/test/unit/helpers/application_helper_test.rb
index 00985c3c..b964b85d 100644
--- a/test/unit/helpers/application_helper_test.rb
+++ b/test/unit/helpers/application_helper_test.rb
@@ -669,6 +669,9 @@ RAW
     assert avatar('jsmith <jsmith@somenet.foo>', :size => 24).include?('s=24')
     # Non-avatar options should be considered html options
     assert avatar('jsmith <jsmith@somenet.foo>', :title => 'John Smith').include?('title="John Smith"')
+    # The default class of the img tag should be gravatar
+    assert avatar('jsmith <jsmith@somenet.foo>').include?('class="gravatar"')
+    assert !avatar('jsmith <jsmith@somenet.foo>', :class => 'picture').include?('class="gravatar"')
     assert_nil avatar('jsmith')
     assert_nil avatar(nil)