diff --git a/docs/oidc-client-ts.api.md b/docs/oidc-client-ts.api.md
index 4216e4d6a..79ce1114d 100644
--- a/docs/oidc-client-ts.api.md
+++ b/docs/oidc-client-ts.api.md
@@ -5,7 +5,7 @@
 ```ts
 
 // @public (undocumented)
-export type AccessTokenCallback = (...ev: unknown[]) => void;
+export type AccessTokenCallback = (...ev: unknown[]) => (Promise<void> | void);
 
 // @public (undocumented)
 export class AccessTokenEvents {
diff --git a/src/AccessTokenEvents.ts b/src/AccessTokenEvents.ts
index 87419055c..90c95104e 100644
--- a/src/AccessTokenEvents.ts
+++ b/src/AccessTokenEvents.ts
@@ -7,7 +7,7 @@ import type { User } from "./User";
 /**
  * @public
  */
-export type AccessTokenCallback = (...ev: unknown[]) => void;
+export type AccessTokenCallback = (...ev: unknown[]) => (Promise<void> | void);
 
 /**
  * @public