lib/mongo/collection/view/builder/op_query.rb in mongo-2.4.3 vs lib/mongo/collection/view/builder/op_query.rb in mongo-2.5.0.beta

@@ -66,10 +66,10 @@
           def requires_special_filter?
             !modifiers.empty? || cluster.sharded?
           end
 
           def read_pref_formatted
-            @read_formatted ||= read.to_mongos
+            @read_formatted ||= ServerSelector.get(read).to_mongos if read
           end
 
           def special_filter
             sel = BSON::Document.new(:$query => filter).merge!(modifiers)
             sel[:$readPreference] = read_pref_formatted unless read_pref_formatted.nil?