diff --git a/activesupport/lib/active_support/deprecation.rb b/activesupport/lib/active_support/deprecation.rb
index 77c00f5a67..2e92cbfbf3 100644
--- a/activesupport/lib/active_support/deprecation.rb
+++ b/activesupport/lib/active_support/deprecation.rb
@@ -48,12 +48,11 @@ module ActiveSupport
     end
 
     module Assertions
-      def assert_deprecated(regexp = nil, &block)
+      def assert_deprecated(match = nil, &block)
         last = with_last_message_tracking_deprecation_behavior(&block)
         assert last, "Expected a deprecation warning within the block but received none"
-        if regexp
-          assert_match regexp, last, "Deprecation warning didn't match #{regexp}: #{last}"
-        end
+        match = Regexp.new(match) unless match.is_a?(Regexp)
+        assert_match match, last, "Deprecation warning didn't match #{match}: #{last}"
       end
 
       def assert_not_deprecated(&block)
@@ -72,6 +71,26 @@ module ActiveSupport
           ActiveSupport::Deprecation.behavior = old_behavior
         end
     end
+
+    # Stand-in for @request, @attributes, etc.
+    class DeprecatedInstanceVariableProxy
+      instance_methods.each { |m| undef_method m unless m =~ /^__/ }
+
+      def initialize(instance, method, var = "@#{method}")
+        @instance, @method, @var = instance, method, var
+        deprecation_warning :initialize, caller
+      end
+
+      private
+        def deprecation_warning(called, callstack)
+          ActiveSupport::Deprecation.warn("Using #{@var} directly is deprecated - call #{@method} instead.", callstack)
+        end
+
+        def method_missing(called, *args, &block)
+          deprecation_warning called, caller
+          @instance.__send__(@method).__send__(called, *args, &block)
+        end
+    end
   end
 end
 
diff --git a/activesupport/test/deprecation_test.rb b/activesupport/test/deprecation_test.rb
index 5fb0c5b042..48506656a5 100644
--- a/activesupport/test/deprecation_test.rb
+++ b/activesupport/test/deprecation_test.rb
@@ -1,6 +1,13 @@
 require File.dirname(__FILE__) + '/abstract_unit'
 
 class Deprecatee
+  def initialize
+    @request = ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(self, :request)
+    @_request = 'there we go'
+  end
+  def request; @_request end
+  def old_request; @request end
+
   def partially(foo = nil)
     ActiveSupport::Deprecation.warn 'calling with foo=nil is out' if foo.nil?
   end
@@ -57,4 +64,13 @@ class DeprecationTest < Test::Unit::TestCase
     ActiveSupport::Deprecation.behavior = nil
     assert_deprecated(/foo=nil/) { @dtc.partially }
   end
+
+  def test_deprecated_instance_variable_proxy
+    assert_not_deprecated { @dtc.request.size }
+
+    assert_deprecated('Using @request directly is deprecated - call request instead.') do
+      assert_equal @dtc.request.size, @dtc.old_request.size
+      assert_equal @dtc.request.to_s, @dtc.old_request.to_s
+    end
+  end
 end