diff --git a/apis/v1beta1/shared_types.go b/apis/v1beta1/shared_types.go
index 2cd09f0832..f973e4b329 100644
--- a/apis/v1beta1/shared_types.go
+++ b/apis/v1beta1/shared_types.go
@@ -215,6 +215,7 @@ const (
 	// * "NoMatchingListenerHostname"
 	// * "NoMatchingParent"
 	// * "UnsupportedValue"
+	// * "ParentRefNotPermitted"
 	//
 	// Possible reasons for this condition to be Unknown are:
 	//
@@ -248,6 +249,11 @@ 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"