diff --git a/index.d.ts b/index.d.ts
index 20406719dd..ed9f858f34 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -138,7 +138,7 @@ export interface CancelStatic {
 }
 
 export interface Cancel {
-  message: string;
+  message: string | undefined;
 }
 
 export interface Canceler {