diff --git a/src/hooks.ts b/src/hooks.ts
index 69e73e4..58a4a7b 100644
--- a/src/hooks.ts
+++ b/src/hooks.ts
@@ -66,8 +66,12 @@ export class AdapterHookable {
         };
       }
     } catch (error) {
-      if (error instanceof Response) {
-        return { context, endResponse: error };
+      const errResponse = (error as { response: Response }).response || error;
+      if (errResponse instanceof Response) {
+        return {
+          context,
+          endResponse: errResponse,
+        };
       }
       throw error;
     }
@@ -96,6 +100,8 @@ export type UpgradeRequest =
       headers: Headers;
     };
 
+export type UpgradeError = Response | { readonly response: Response };
+
 export interface Hooks {
   /** Upgrading */
   /**
diff --git a/test/fixture/_shared.ts b/test/fixture/_shared.ts
index 077336d..9afe6c2 100644
--- a/test/fixture/_shared.ts
+++ b/test/fixture/_shared.ts
@@ -58,11 +58,15 @@ export function createDemo<T extends Adapter<any, any>>(
     },
     upgrade(req) {
       if (req.url.endsWith("?unauthorized")) {
-        return new Response("unauthorized", {
-          status: 401,
-          statusText: "Unauthorized",
-          headers: { "x-error": "unauthorized" },
-        });
+        throw {
+          get response() {
+            return new Response("unauthorized", {
+              status: 401,
+              statusText: "Unauthorized",
+              headers: { "x-error": "unauthorized" },
+            });
+          },
+        };
       }
       req.context.test = "1";
       return {