diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index bc5824104e801dab023202d5ff37d50ebd14c2ae..937efe395fa3f94340247abd3f8ea1b57b600fdf 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -1,4 +1,5 @@
 require 'active_support/core_ext/class/attribute'
+require 'active_support/core_ext/module/deprecation'
 
 module ActiveRecord
   # = Active Record Reflection
@@ -200,6 +201,11 @@ def foreign_key
         @foreign_key ||= options[:foreign_key] || derive_foreign_key
       end
 
+      def primary_key_name
+        foreign_key
+      end
+      deprecate :primary_key_name => :foreign_key
+
       def foreign_type
         @foreign_type ||= options[:foreign_type] || "#{name}_type"
       end
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index 081e3cc861212d26d8cecab148b54ca7a927e5b3..d75bc3982e91b8530391f15a970791d42e0519c0 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -248,6 +248,18 @@ def test_never_validate_association_if_explicit
     assert !AssociationReflection.new(:has_and_belongs_to_many, :clients, { :autosave => true, :validate => false }, Firm).validate?
   end
 
+  def test_foreign_key
+    assert_equal "author_id", Author.reflect_on_association(:posts).foreign_key.to_s
+    assert_equal "category_id", Post.reflect_on_association(:categorizations).foreign_key.to_s
+  end
+
+  def test_primary_key_name
+    assert_deprecated do
+      assert_equal "author_id", Author.reflect_on_association(:posts).primary_key_name.to_s
+      assert_equal "category_id", Post.reflect_on_association(:categorizations).primary_key_name.to_s
+    end
+  end
+
   private
     def assert_reflection(klass, association, options)
       assert reflection = klass.reflect_on_association(association)
diff --git a/activesupport/lib/active_support/deprecation.rb b/activesupport/lib/active_support/deprecation.rb
index e3e63ce316e7cda6b2f5e787c6f1e928b522faba..ce0775a690a7dc80e8d20f8a06213b50aa694706 100644
--- a/activesupport/lib/active_support/deprecation.rb
+++ b/activesupport/lib/active_support/deprecation.rb
@@ -9,7 +9,7 @@ class << self
       # The version the deprecated behavior will be removed, by default.
       attr_accessor :deprecation_horizon
     end
-    self.deprecation_horizon = '3.0'
+    self.deprecation_horizon = '3.1'
 
     # By default, warnings are not silenced and debugging is off.
     self.silenced = false