diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 5357255bad6dd05c1072652e0f6aa9d75e678ebc..15c6bc1b4aea92848ca3f457ef7dc5a12b5b9fc0 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1750,7 +1750,7 @@ def all_attributes_exists?(attribute_names)
         def attribute_condition(argument)
           case argument
             when nil   then "IS ?"
-            when Array, ActiveRecord::Associations::AssociationCollection then "IN (?)"
+            when Array, ActiveRecord::Associations::AssociationCollection, ActiveRecord::NamedScope::Scope then "IN (?)"
             when Range then "BETWEEN ? AND ?"
             else            "= ?"
           end
diff --git a/activerecord/test/cases/named_scope_test.rb b/activerecord/test/cases/named_scope_test.rb
index 7cc51f5d6880e43a052afa83c8cde70aa7d40a3c..db31ddb29338a3d20faf50ce8d94ff406e235b12 100644
--- a/activerecord/test/cases/named_scope_test.rb
+++ b/activerecord/test/cases/named_scope_test.rb
@@ -4,6 +4,7 @@
 require 'models/comment'
 require 'models/reply'
 require 'models/author'
+require 'models/developer'
 
 class NamedScopeTest < ActiveRecord::TestCase
   fixtures :posts, :authors, :topics, :comments, :author_addresses
@@ -242,4 +243,8 @@ def test_should_build_with_proxy_options_chained
   def test_find_all_should_behave_like_select
     assert_equal Topic.base.select(&:approved), Topic.base.find_all(&:approved)
   end
+
+  def test_should_use_where_in_query_for_named_scope
+    assert_equal Developer.find_all_by_name('Jamis'), Developer.find_all_by_id(Developer.jamises)
+  end
 end
diff --git a/activerecord/test/models/developer.rb b/activerecord/test/models/developer.rb
index 9f26cacdecb707b7e4cdc35ef382adde204049ba..c08476f728fb66eaeff965d8053854e07f424ef0 100644
--- a/activerecord/test/models/developer.rb
+++ b/activerecord/test/models/developer.rb
@@ -43,6 +43,8 @@ def find_least_recent
 
   has_many :audit_logs
 
+  named_scope :jamises, :conditions => {:name => 'Jamis'}
+
   validates_inclusion_of :salary, :in => 50000..200000
   validates_length_of    :name, :within => 3..20