diff --git a/lib/remote_storage/riak.rb b/lib/remote_storage/riak.rb
index ac8f927..f812134 100644
--- a/lib/remote_storage/riak.rb
+++ b/lib/remote_storage/riak.rb
@@ -156,12 +156,13 @@ module RemoteStorage
     def log_object_size(user, directory, new_size=0, old_size=0)
       category = extract_category(directory)
       info = info_bucket.get_or_new("usage:size:#{user}:#{category}")
-
       info.content_type = "text/plain"
+
       size = -old_size + new_size
       size += info.data.to_i
 
       info.data = size.to_s
+      info.indexes.merge!({:user_id_bin => [user]})
       info.store
     end
 
diff --git a/spec/riak_spec.rb b/spec/riak_spec.rb
index d9324bf..f43dcf4 100644
--- a/spec/riak_spec.rb
+++ b/spec/riak_spec.rb
@@ -111,8 +111,11 @@ describe "App with Riak backend" do
           data_bucket.get("jimmy:documents:bar").content_type.must_equal "text/plain; charset=utf-8"
         end
 
-        it "increases the overall category size" do
+        it "increases the usage size counter" do
           info_bucket.get("usage:size:jimmy:documents").data.must_equal "35"
+
+          indexes = info_bucket.get("usage:size:jimmy:documents").indexes
+          indexes["user_id_bin"].must_include "jimmy"
         end
 
         it "indexes the data set" do