diff --git a/lib/metamorpher/builders/ast/builder.rb b/lib/metamorpher/builders/ast/builder.rb
index <HASH>..<HASH> 100644
--- a/lib/metamorpher/builders/ast/builder.rb
+++ b/lib/metamorpher/builders/ast/builder.rb
@@ -2,6 +2,7 @@ require "metamorpher/builders/ast/literal_builder"
 require "metamorpher/builders/ast/variable_builder"
 require "metamorpher/builders/ast/greedy_variable_builder"
 require "metamorpher/builders/ast/derivation_builder"
+require "forwardable"
 
 module Metamorpher
   module Builders
diff --git a/spec/integration/ruby/refactorer_spec.rb b/spec/integration/ruby/refactorer_spec.rb
index <HASH>..<HASH> 100644
--- a/spec/integration/ruby/refactorer_spec.rb
+++ b/spec/integration/ruby/refactorer_spec.rb
@@ -1,4 +1,5 @@
 require "metamorpher"
+require "tempfile"
 
 describe "Refactorer" do
   describe "for Ruby" do
Fix dependencies on components that are no longer in Ruby core.