diff --git a/manifests/alias.pp b/manifests/alias.pp
index 60009535..c0f56d1d 100644
--- a/manifests/alias.pp
+++ b/manifests/alias.pp
@@ -56,6 +56,9 @@
   # Validate our booleans
   validate_bool($noaliasrouting)
   validate_bool($userctl)
+  # Validate our regular expressions
+  $states = [ '^up$', '^down$' ]
+  validate_re($ensure, $states, '$ensure must be either "up" or "down".')
 
   include '::network'