diff --git a/lib/memoist.rb b/lib/memoist.rb
index 0b8558f..c1e5058 100644
--- a/lib/memoist.rb
+++ b/lib/memoist.rb
@@ -31,7 +31,7 @@ def self.memoist_eval(klass, *args, &block)
   end
 
   def self.extract_reload!(method, args)
-    if args.length == method.arity + 1 && (args.last == true || args.last == :reload)
+    if args.length == method.arity.abs + 1 && (args.last == true || args.last == :reload)
       reload = args.pop
     end
     reload
diff --git a/test/memoist_test.rb b/test/memoist_test.rb
index bc21516..346cc6d 100644
--- a/test/memoist_test.rb
+++ b/test/memoist_test.rb
@@ -70,6 +70,26 @@ def age
 
     memoize :name, :age
 
+    def sleep(hours = 8)
+      @counter.call(:sleep)
+      hours
+    end
+    memoize :sleep
+
+    def sleep_calls
+      @counter.count(:sleep)
+    end
+
+    def update_attributes(options = {})
+      @counter.call(:update_attributes)
+      true
+    end
+    memoize :update_attributes
+
+    def update_attributes_calls
+      @counter.count(:update_attributes)
+    end
+
     protected
 
     def memoize_protected_test
@@ -167,6 +187,28 @@ def test_memoization
     assert_equal 1, @person.name_calls
   end
 
+  def test_memoize_with_optional_arguments
+    assert_equal 4, @person.sleep(4)
+    assert_equal 1, @person.sleep_calls
+
+    3.times { assert_equal 4, @person.sleep(4) }
+    assert_equal 1, @person.sleep_calls
+
+    3.times { assert_equal 4, @person.sleep(4, :reload) }
+    assert_equal 4, @person.sleep_calls
+  end
+
+  def test_memoize_with_options_hash
+    assert_equal true, @person.update_attributes(:age => 21, :name => 'James')
+    assert_equal 1, @person.update_attributes_calls
+
+    3.times { assert_equal true, @person.update_attributes(:age => 21, :name => 'James') }
+    assert_equal 1, @person.update_attributes_calls
+
+    3.times { assert_equal true, @person.update_attributes({:age => 21, :name => 'James'}, :reload) }
+    assert_equal 4, @person.update_attributes_calls
+  end
+
   def test_memoization_with_punctuation
     assert_equal true, @person.name?