diff --git a/app/helpers/avatar_helper.rb b/app/helpers/avatar_helper.rb
index c17ccadf..abaa7950 100644
--- a/app/helpers/avatar_helper.rb
+++ b/app/helpers/avatar_helper.rb
@@ -34,7 +34,7 @@ module AvatarHelper
     if source.nil? 
       return File.join(relative_path,'AnonymousUser','0')      
     end
-    if File.exist?(disk_filename(source.class,source.id))
+    if source.class && source.id && File.exist?(disk_filename(source.class,source.id))
       avatar_image(source)
     else
       File.join(relative_path,avatar_directory(source.class),'0')