diff --git a/packages/astro/src/@types/astro.ts b/packages/astro/src/@types/astro.ts
index dfd85e9b0..6e77ba20c 100644
--- a/packages/astro/src/@types/astro.ts
+++ b/packages/astro/src/@types/astro.ts
@@ -869,8 +869,6 @@ export type Params = Record<string, string | number | undefined>;
 
 export type Props = Record<string, unknown>;
 
-type Body = string;
-
 export interface AstroAdapter {
 	name: string;
 	serverEntrypoint?: string;
@@ -878,16 +876,18 @@ export interface AstroAdapter {
 	args?: any;
 }
 
+type Body = string;
+
 export interface APIContext {
 	params: Params;
 	request: Request;
 }
 
-export interface EndpointOutput<Output extends Body = Body> {
-	body: Output;
+export interface EndpointOutput {
+	body: Body;
 }
 
-export type APIRoute = (context: APIContext) => EndpointOutput | Response;
+export type APIRoute = (context: APIContext) => EndpointOutput | Response | Promise<EndpointOutput | Response>;
 
 export interface EndpointHandler {
 	[method: string]: APIRoute | ((params: Params, request: Request) => EndpointOutput | Response);