diff --git a/aasm.gemspec b/aasm.gemspec
index ca3a77c..0f85bad 100644
--- a/aasm.gemspec
+++ b/aasm.gemspec
@@ -1,4 +1,4 @@
-PKG_FILES = ["CHANGELOG", "MIT-LICENSE", "Rakefile", "README.rdoc", "TODO", "lib/aasm.rb", "lib/event.rb", "lib/persistence/active_record_persistence.rb", "lib/persistence.rb", "lib/state.rb", "lib/state_transition.rb", "lib/version.rb", "doc/jamis.rb"]
+PKG_FILES = ["CHANGELOG", "MIT-LICENSE", "Rakefile", "README.rdoc", "TODO", "lib/aasm.rb", "lib/event.rb", "lib/persistence/active_record_persistence.rb", "lib/persistence.rb", "lib/state.rb", "lib/state_machine.rb", "lib/state_transition.rb", "lib/version.rb", "doc/jamis.rb"]
 
 Gem::Specification.new do |s|
   s.name = 'aasm'