diff --git a/packages/inertia/src/types.ts b/packages/inertia/src/types.ts
index 52396f65f..10ed082a3 100644
--- a/packages/inertia/src/types.ts
+++ b/packages/inertia/src/types.ts
@@ -3,7 +3,7 @@ import { AxiosResponse, CancelTokenSource } from 'axios'
 export type Errors = Record<string, string>
 export type ErrorBag = Record<string, Errors>
 
-export type FormDataConvertible = Array<FormDataConvertible>|Blob|FormDataEntryValue|Date|boolean|number|null
+export type FormDataConvertible = Array<FormDataConvertible>|Blob|FormDataEntryValue|Date|boolean|number|null|undefined
 
 export enum Method {
   GET = 'get',