diff --git a/manifests/object/apply_notification_to_host.pp b/manifests/object/apply_notification_to_host.pp
index 56dc001..8cdb17d 100644
--- a/manifests/object/apply_notification_to_host.pp
+++ b/manifests/object/apply_notification_to_host.pp
@@ -42,7 +42,7 @@ define icinga2::object::apply_notification_to_host (
   validate_array($user_groups)
   validate_hash($times)
   if $interval {
-    validate_re($interval, '^\d$')
+    validate_string($interval)
   }
   if $period {
     validate_string($period)
diff --git a/manifests/object/apply_notification_to_service.pp b/manifests/object/apply_notification_to_service.pp
index bda9a16..b265c9f 100644
--- a/manifests/object/apply_notification_to_service.pp
+++ b/manifests/object/apply_notification_to_service.pp
@@ -44,7 +44,7 @@ define icinga2::object::apply_notification_to_service (
   validate_array($user_groups)
   validate_hash($times)
   if $interval {
-    validate_re($interval, '^\d$')
+    validate_string($interval)
   }
   if $period {
     validate_string($period)