diff --git a/dm-core.gemspec b/dm-core.gemspec
index 6921c011..aa942c30 100644
--- a/dm-core.gemspec
+++ b/dm-core.gemspec
@@ -18,8 +18,7 @@ Gem::Specification.new do |gem|
   gem.version       = DataMapper::VERSION
 
   gem.add_runtime_dependency('addressable', '~> 2.2.6')
-  gem.add_runtime_dependency('virtus',      '~> 0.2.0')
-  gem.add_runtime_dependency('backports',   '~> 2.3.0')
+  gem.add_runtime_dependency('virtus',      '~> 0.4.1')
 
   gem.add_development_dependency('rake',  '~> 0.9.2')
   gem.add_development_dependency('rspec', '~> 1.3.2')