diff --git a/manifests/plugins/ml2.pp b/manifests/plugins/ml2.pp
index d931e727a..b94359353 100644
--- a/manifests/plugins/ml2.pp
+++ b/manifests/plugins/ml2.pp
@@ -171,7 +171,7 @@ class neutron::plugins::ml2 (
     warning ('supported_pci_vendor_devs is deprecated, has no effect and will be removed in a future release.')
   }
 
-  if !is_service_default($overlay_ip_version) and !($overlay_ip_version in [4, 6]) {
+  if !is_service_default($overlay_ip_version) and !("${overlay_ip_version}" in ['4', '6']) {
     fail('Invalid IP version for overlay_ip_version')
   }