diff --git a/puppet-syntax.gemspec b/puppet-syntax.gemspec
index 7731acf..85aa771 100644
--- a/puppet-syntax.gemspec
+++ b/puppet-syntax.gemspec
@@ -19,6 +19,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "rake"
+  spec_add_dependency "puppet", ">= 5"
 
   spec.add_development_dependency "pry"
   spec.add_development_dependency "rb-readline"