diff --git a/apis/v1beta1/shared_types.go b/apis/v1beta1/shared_types.go
index 7f70930be4..419e769b6d 100644
--- a/apis/v1beta1/shared_types.go
+++ b/apis/v1beta1/shared_types.go
@@ -214,6 +214,7 @@ const (
 	// * "NotAllowedByListeners"
 	// * "NoMatchingListenerHostname"
 	// * "UnsupportedValue"
+	// * "ParentRefNotPermitted"
 	//
 	// Possible reasons for this condition to be Unknown are:
 	//
@@ -247,6 +248,11 @@ const (
 	// is not recognized.
 	RouteReasonUnsupportedValue RouteConditionReason = "UnsupportedValue"
 
+	// This reason is used with the "Accepted" condition when the route has not
+	// been accepted by a Gateway because it has a cross-namespace parentRef,
+	// but no ReferenceGrant in the other namespace allows such a reference.
+	RouteReasonParentRefNotPermitted RouteConditionReason = "ParentRefNotPermitted"
+
 	// This reason is used with the "Accepted" when a controller has not yet
 	// reconciled the route.
 	RouteReasonPending RouteConditionReason = "Pending"