diff --git a/test/integration/default/controls/pkgs_spec.rb b/test/integration/default/controls/pkgs_spec.rb
index b7ed81c..14b4743 100644
--- a/test/integration/default/controls/pkgs_spec.rb
+++ b/test/integration/default/controls/pkgs_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 control 'Postfix packages' do
   title 'should be installed'
 
diff --git a/test/integration/default/controls/service_spec.rb b/test/integration/default/controls/service_spec.rb
index 6a118cd..9b40c88 100644
--- a/test/integration/default/controls/service_spec.rb
+++ b/test/integration/default/controls/service_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 control 'Postfix service' do
   title 'should be running'