diff --git a/lib/mongoid_sphinx/mongoid/sphinx.rb b/lib/mongoid_sphinx/mongoid/sphinx.rb
index 0b78527..b52aae0 100644
--- a/lib/mongoid_sphinx/mongoid/sphinx.rb
+++ b/lib/mongoid_sphinx/mongoid/sphinx.rb
@@ -1,5 +1,3 @@
-require 'digest'
-
 module Mongoid
   module Sphinx
     extend ActiveSupport::Concern
@@ -94,7 +92,7 @@ def generate_stream
           xml << "<sphinx:field name=\"#{key}\"/>"
         end
         xml << '<sphinx:attr name="class_name" type="string"/>'
-        xml << '<sphinx:attr name="class_filter" type="int" bits="64"/>'
+        xml << '<sphinx:attr name="class_filter" type="int" bits="32"/>'
         search_attributes.each do |key, value|
           xml << "<sphinx:attr name=\"#{key}\" type=\"#{value}\"/>"
         end
@@ -159,7 +157,6 @@ def get_fields(document)
       # override this method to process embedded ids
       def search(query, options = {})
         ids = MongoidSphinx::search(query, options.merge(:class => self))
-        # ids = ids.reject{ |id| id.class_name!=self.to_s }
         ids = ids.map(&:sphinx_id)
         if embedded?
           ids
diff --git a/lib/mongoid_sphinx/search.rb b/lib/mongoid_sphinx/search.rb
index 87b8de9..d29eb3b 100644
--- a/lib/mongoid_sphinx/search.rb
+++ b/lib/mongoid_sphinx/search.rb
@@ -1,3 +1,4 @@
+require 'zlib'
 require 'ostruct'
 
 module MongoidSphinx
@@ -29,7 +30,7 @@ def self.default_client(options={})
   end
 
   def self.class_filter(klass)
-    Digest::MD5.hexdigest(klass.to_s)[0...16].hex
+    Zlib::crc32(klass.to_s) & 0xffffffff
   end
 
   def self.search(query, options = {})
@@ -57,8 +58,7 @@ def self.search_ids(id_range, options = {})
     client.match_mode = :extended
     client.limit = options[:limit] if options.key?(:limit)
     client.max_matches = options[:max_matches] if options.key?(:max_matches)
-    # TODO: I cant get this to work, always returns no results
-    # client.filters << Riddle::Client::Filter.new('class_name', options[:class].name.to_a, false) if options.key?(:class)
+    client.filters << Riddle::Client::Filter.new('class_filter', [class_filter(options[:class])], false) if options.key?(:class)
 
     results = client.query('*')
     process_results(results)