diff --git a/README.md b/README.md
index db60791..c82e7a6 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ I'd much rather ask an object if it was in a list. It just feels like it's the
 right way round:
 
 ```ruby
-thing.in?('Egg', 'Bacon', 'Sausage')
+thing.in?(['Egg', 'Bacon', 'Sausage'])
 ```
 
 ## Installation
@@ -37,10 +37,14 @@ Require Inny and then start testing your objects:
 ```ruby
 require 'inny'
 
-object.in?('Foo', 'Bar')
+object.in?(['Foo', 'Bar'])
+
+'Foo'.in?('Foobar')
+
+5.in?(1..10)
 
 list = [1, 2, 3]
-puts "Yay!" if 2.in?(*list)
+puts "Yay!" if 2.in?(list)
 ```
 
 ## Development
diff --git a/lib/inny.rb b/lib/inny.rb
index ef3c41e..b4fdd70 100644
--- a/lib/inny.rb
+++ b/lib/inny.rb
@@ -1,8 +1,12 @@
 require "inny/version"
 
 module Inny
-  def in?(*list)
-    list.include?(self)
+  def in?(object)
+    begin
+      object.include?(self)
+    rescue NoMethodError
+      raise ArgumentError.new("The parameter passed to #in? must respond to #include?")
+    end
   end
 end
 
diff --git a/lib/inny/version.rb b/lib/inny/version.rb
index 0596b70..00a63fe 100644
--- a/lib/inny/version.rb
+++ b/lib/inny/version.rb
@@ -1,3 +1,3 @@
 module Inny
-  VERSION = "1.0.0"
+  VERSION = "2.0.0"
 end