nanoc.gemspec in nanoc-4.2.3 vs nanoc.gemspec in nanoc-4.2.4

@@ -24,8 +24,9 @@
 
   s.required_ruby_version = '>= 2.1.0'
 
   s.add_runtime_dependency('cri', '~> 2.3')
   s.add_runtime_dependency('hamster', '~> 3.0')
+  s.add_runtime_dependency('ref', '~> 2.0')
 
   s.add_development_dependency('bundler', '>= 1.7.10', '< 2.0')
 end