diff --git a/lib/reform/contract.rb b/lib/reform/contract.rb
index <HASH>..<HASH> 100644
--- a/lib/reform/contract.rb
+++ b/lib/reform/contract.rb
@@ -40,6 +40,10 @@ module Reform
     require "reform/validation"
     include Reform::Validation # ::validates and #valid?
 
+    # FIXME: this is only for #to_nested_hash, #sync shouldn't be part of Contract.
+    require "disposable/twin/sync"
+    include Disposable::Twin::Sync
+
 
 
     # module ValidatesWarning
diff --git a/test/validate_test.rb b/test/validate_test.rb
index <HASH>..<HASH> 100644
--- a/test/validate_test.rb
+++ b/test/validate_test.rb
@@ -50,7 +50,7 @@ class ContractValidateTest < MiniTest::Spec
     album.name = nil
 
     form.validate.must_equal false
-    form.errors.messages.inspect.must_equal "{:name=>[\"must be filled\"], :\"songs.composer.name\"=>[\"must be filled\"]}"
+    form.errors.messages.inspect.must_equal "{:name=>[\"is missing\"], :\"songs.composer.name\"=>[\"is missing\"]}"
   end
 end
include Sync into Contract to get #to_nested_hash for #validate. this is not ideal as Contract is meant to be validate-only. might refactor.