diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index e40b8d47608a4..f1b6f3003aae8 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Fixed that validates_uniqueness_of used 'id' instead of defined primary key #406
+
 * Fixed that the overwritten respond_to? method didn't take two parameters like the original #391
 
 * Added HasManyAssociation#count that works like Base#count #413 [intinig]
diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index a451e4299aefa..5e9608f9db197 100755
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -213,9 +213,9 @@ def validates_uniqueness_of(*attr_names)
 
         for attr_name in attr_names
           if scope = configuration[:scope]
-            class_eval(%(validate %{errors.add('#{attr_name}', '#{configuration[:message]}') if self.class.find_first(new_record? ? ['#{attr_name} = ? AND #{scope} = ?', #{attr_name}, #{scope}] : ["#{attr_name} = ? AND id <> ? AND #{scope} = ?", #{attr_name}, id, #{scope}])}))
+            class_eval(%(validate %{errors.add('#{attr_name}', '#{configuration[:message]}') if self.class.find_first(new_record? ? ['#{attr_name} = ? AND #{scope} = ?', #{attr_name}, #{scope}] : ["#{attr_name} = ? AND \#{primary_key} <> ? AND #{scope} = ?", #{attr_name}, id, #{scope}])}))
           else
-            class_eval(%(validate %{errors.add('#{attr_name}', '#{configuration[:message]}') if self.class.find_first(new_record? ? ['#{attr_name} = ?', #{attr_name}] : ["#{attr_name} = ? AND id <> ?", #{attr_name}, id])}))
+            class_eval(%(validate %{errors.add('#{attr_name}', '#{configuration[:message]}') if self.class.find_first(new_record? ? ['#{attr_name} = ?', #{attr_name}] : ["#{attr_name} = ? AND \#{primary_key} <> ?", #{attr_name}, id])}))
           end
         end
       end