diff --git a/types/hapi/index.d.ts b/types/hapi/index.d.ts
index 3e323f8c44..ec2359ed5a 100644
--- a/types/hapi/index.d.ts
+++ b/types/hapi/index.d.ts
@@ -1428,7 +1428,7 @@ export interface RouteOptionsPreObject {
     /**
      * key name used to assign the response of the method to in request.pre and request.preResponses.
      */
-    assign: string;
+    assign?: string;
     /**
      * A failAction value which determine what to do when a pre-handler method throws an error. If assign is specified and the failAction setting is not 'error', the error will be assigned.
      */