diff --git a/lib/ransack/nodes/attribute.rb b/lib/ransack/nodes/attribute.rb
index 3e6792e..20d9ca6 100644
--- a/lib/ransack/nodes/attribute.rb
+++ b/lib/ransack/nodes/attribute.rb
@@ -19,7 +19,8 @@ module Ransack
       end
 
       def valid?
-        bound? && attr
+        bound? && attr &&
+          context.klassify(parent).ransackable_attributes.include?(attr_name)
       end
 
       def type
@@ -50,4 +51,4 @@ module Ransack
 
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/ransack/adapters/active_record/base_spec.rb b/spec/ransack/adapters/active_record/base_spec.rb
index 302da17..90c65f5 100644
--- a/spec/ransack/adapters/active_record/base_spec.rb
+++ b/spec/ransack/adapters/active_record/base_spec.rb
@@ -59,9 +59,14 @@ module Ransack
             s.result.to_sql.should_not match /ORDER BY "people"."name" \|\| "only_search" \|\| "people"."name" ASC/
           end
 
+          it 'allows search by "only_search" field' do
+            s = Person.search(:only_search_eq => 'htimS cirA')
+            s.result.to_sql.should match /WHERE "people"."name" \|\| "only_search" \|\| "people"."name" = 'htimS cirA'/
+          end
+
           it "can't be searched by 'only_sort'" do
             s = Person.search(:only_sort_eq => 'htimS cirA')
-            s.result.to_sql.should_not match /'htimS cirA'/
+            s.result.to_sql.should_not match /WHERE "people"."name" \|\| "only_sort" \|\| "people"."name" = 'htimS cirA'/
           end
         end
 
diff --git a/spec/support/schema.rb b/spec/support/schema.rb
index 601d054..e406392 100644
--- a/spec/support/schema.rb
+++ b/spec/support/schema.rb
@@ -29,11 +29,11 @@ class Person < ActiveRecord::Base
     Arel::Nodes::InfixOperation.new('||', parent.table[:name], parent.table[:name])
   end
 
-  ransacker :only_search, :formatter => proc {|v| "only_search#{v}"} do |parent|
+  ransacker :only_search do |parent|
     Arel::Nodes::InfixOperation.new('|| "only_search" ||', parent.table[:name], parent.table[:name])
   end
 
-  ransacker :only_sort, :formatter => proc {|v| "only_sort#{v}"} do |parent|
+  ransacker :only_sort do |parent|
     Arel::Nodes::InfixOperation.new('|| "only_sort" ||', parent.table[:name], parent.table[:name])
   end