diff --git a/activesupport/lib/active_support/memoizable.rb b/activesupport/lib/active_support/memoizable.rb
index 4786fd6e0b..cd5c01cda2 100644
--- a/activesupport/lib/active_support/memoizable.rb
+++ b/activesupport/lib/active_support/memoizable.rb
@@ -1,5 +1,9 @@
 module ActiveSupport
   module Memoizable
+    MEMOIZED_IVAR = Proc.new do |symbol|
+      "@_memoized_#{symbol.to_s.sub(/\?\Z/, '_query').sub(/!\Z/, '_bang')}".to_sym
+    end
+
     module Freezable
       def self.included(base)
         base.class_eval do
@@ -20,7 +24,7 @@ module ActiveSupport
             if method(m).arity == 0
               __send__($1)
             else
-              ivar = :"@_memoized_#{$1}"
+              ivar = MEMOIZED_IVAR.call($1)
               instance_variable_set(ivar, {})
             end
           end
@@ -30,7 +34,7 @@ module ActiveSupport
       def unmemoize_all
         methods.each do |m|
           if m.to_s =~ /^_unmemoized_(.*)/
-            ivar = :"@_memoized_#{$1}"
+            ivar = MEMOIZED_IVAR.call($1)
             instance_variable_get(ivar).clear if instance_variable_defined?(ivar)
           end
         end
@@ -40,7 +44,7 @@ module ActiveSupport
     def memoize(*symbols)
       symbols.each do |symbol|
         original_method = :"_unmemoized_#{symbol}"
-        memoized_ivar = :"@_memoized_#{symbol.to_s.sub(/\?\Z/, '_query').sub(/!\Z/, '_bang')}"
+        memoized_ivar = MEMOIZED_IVAR.call(symbol)
 
         class_eval <<-EOS, __FILE__, __LINE__
           include Freezable
diff --git a/activesupport/test/memoizable_test.rb b/activesupport/test/memoizable_test.rb
index 135d56f14a..a78ebd9425 100644
--- a/activesupport/test/memoizable_test.rb
+++ b/activesupport/test/memoizable_test.rb
@@ -100,6 +100,11 @@ uses_mocha 'Memoizable' do
 
     def test_memoization_with_punctuation
       assert_equal true, @person.name?
+
+      assert_nothing_raised(NameError) do
+        @person.memoize_all
+        @person.unmemoize_all
+      end
     end
 
     def test_memoization_with_nil_value