diff --git a/lib/prawn/js.rb b/lib/prawn/js.rb
index 8008692..1858749 100644
--- a/lib/prawn/js.rb
+++ b/lib/prawn/js.rb
@@ -5,6 +5,7 @@
 # Copyright March 2009, James Healy. All Rights Reserved.
 #
 # This is free software. Please see the LICENSE file for details.
+require 'pdf/core/utils'
 
 module Prawn
   module JS
@@ -81,11 +82,11 @@ def aa
     # See section 3.6.3 and table 3.28 in the PDF spec.
     #
     def javascript
-      names.data[:JavaScript] ||= ref!(Prawn::NameTree::Node.new(self, NAME_TREE_CHILDREN_LIMIT))
+      names.data[:JavaScript] ||= ref!(PDF::Core::NameTree::Node.new(self, NAME_TREE_CHILDREN_LIMIT))
     end
 
   end
 end
 
-require 'prawn/document'
-Prawn::Document.send(:include, Prawn::JS)
+require 'pdf/core'
+PDF::Core::Renderer.send(:include, Prawn::JS)
diff --git a/prawn-js.gemspec b/prawn-js.gemspec
index 6352474..45bae40 100644
--- a/prawn-js.gemspec
+++ b/prawn-js.gemspec
@@ -18,5 +18,5 @@ Gem::Specification.new do |s|
   s.require_paths = ["lib"]
   s.rubyforge_project = %q{prawn}
   s.summary = %q{A small extension to prawn that makes it possible to embed JavaScript fragment in  your document that respond to events.}
-  s.add_dependency('prawn-core', '>=0.6.1')
+  s.add_dependency('pdf-core', '>=0.7.0')
 end