diff --git a/packages/start/api/index.ts b/packages/start/api/index.ts
index 398dce323..2e81be321 100644
--- a/packages/start/api/index.ts
+++ b/packages/start/api/index.ts
@@ -8,6 +8,12 @@ import { MatchRoute, Method, Route } from "./types";
 // @ts-ignore
 var api = $API_ROUTES;
 
+// used by the compiled configuration of routes
+// @ts-ignore
+function methodNotAllowed()  {
+  return new Response(null, { status: 405 });
+}
+
 // This is copied from https://github.com/solidjs/solid-router/blob/main/src/utils.ts
 function expandOptionals(pattern: string): string[] {
   let match = /(\/?\:[^\/]+)\?/.exec(pattern);
@@ -95,3 +101,4 @@ export function isApiRequest(request: Request) {
 
 export * from "../server/responses";
 export type { APIEvent } from "./types";
+
diff --git a/packages/start/entry-server/index.ts b/packages/start/entry-server/index.ts
index 25a1c2a46..648c79dde 100644
--- a/packages/start/entry-server/index.ts
+++ b/packages/start/entry-server/index.ts
@@ -1,4 +1,4 @@
-export { composeMiddleware, createHandler, default as StartServer } from "./StartServer";
+export { default as StartServer, composeMiddleware, createHandler } from "./StartServer";
 export type { Middleware, MiddlewareFn, MiddlewareInput } from "./StartServer";
 
 import { JSX } from "solid-js";
@@ -21,8 +21,8 @@ export const render = (
   }
 ) =>
   composeMiddleware([
-    apiRoutes,
     inlineServerFunctions,
+    apiRoutes,
     import.meta.env.START_SSR === "async"
       ? _renderAsync(fn, options)
       : import.meta.env.START_SSR === "streaming"
@@ -37,7 +37,7 @@ export const renderAsync = (
     nonce?: string;
     renderId?: string;
   }
-) => composeMiddleware([apiRoutes, inlineServerFunctions, _renderAsync(fn, options)]);
+) => composeMiddleware([inlineServerFunctions, apiRoutes, _renderAsync(fn, options)]);
 
 export const renderStream = (
   fn: (context: PageEvent) => JSX.Element,
@@ -46,7 +46,7 @@ export const renderStream = (
     nonce?: string;
     renderId?: string;
   }
-) => composeMiddleware([apiRoutes, inlineServerFunctions, _renderStream(fn, options)]);
+) => composeMiddleware([inlineServerFunctions, apiRoutes, _renderStream(fn, options)]);
 
 export const renderSync = (
   fn: (context: PageEvent) => JSX.Element,
@@ -55,4 +55,4 @@ export const renderSync = (
     nonce?: string;
     renderId?: string;
   }
-) => composeMiddleware([apiRoutes, inlineServerFunctions, _renderSync(fn, options)]);
+) => composeMiddleware([inlineServerFunctions, apiRoutes, _renderSync(fn, options)]);
diff --git a/packages/start/fs-router/router.js b/packages/start/fs-router/router.js
index f98c16d7d..c1148372b 100644
--- a/packages/start/fs-router/router.js
+++ b/packages/start/fs-router/router.js
@@ -379,7 +379,7 @@ export function stringifyPageRoutes(
 
 export function stringifyAPIRoutes(
   /** @type {(RouteConfig)[]} */ flatRoutes,
-  /** @type {{ lazy?: boolean }} */ options = {}
+  /** @type {{ lazy?: boolean, islandsRouter?: boolean }} */ options = {}
 ) {
   const jsFile = jsCode();
 
@@ -393,12 +393,15 @@ export function stringifyAPIRoutes(
         .map(
           i =>
             `{\n${[
-              ...API_METHODS.filter(j => i.apiPath?.[j]).map(
-                v =>
-                  i.apiPath != null &&
-                  `${v}: ${jsFile.addNamedImport(v, path.posix.resolve(i.apiPath[v]))}`
-              ),
-              i.componentPath ? `GET: "skip"` : undefined,
+              ...API_METHODS.map(v => {
+                if (v === "GET" && i.componentPath)
+                  return `${v}: "skip"`;
+                if (v === "POST" && options.islandsRouter && i.componentPath)
+                  return `${v}: "skip"`;
+                else if (i.apiPath?.[v])
+                  return `${v}: ${jsFile.addNamedImport(v, path.posix.resolve(i.apiPath[v]))}`;
+                return `${v}: methodNotAllowed`;
+              }),
               `path: ${JSON.stringify(i.path)}`
             ]
               .filter(Boolean)
diff --git a/packages/start/vite/plugin.js b/packages/start/vite/plugin.js
index 59afaa670..c01c4bfe2 100644
--- a/packages/start/vite/plugin.js
+++ b/packages/start/vite/plugin.js
@@ -440,7 +440,10 @@ function solidStartFileSystemRouter(options) {
         return {
           code: code.replace(
             "var api = $API_ROUTES;",
-            stringifyAPIRoutes(config.solidOptions.router.getFlattenedApiRoutes(true), { lazy })
+            stringifyAPIRoutes(
+              config.solidOptions.router.getFlattenedApiRoutes(true), 
+              { lazy, islandsRouter: !!config.solidOptions.experimental?.islandsRouter }
+            )
           )
         };
       }
diff --git a/test/api-routes-test.ts b/test/api-routes-test.ts
index 260555751..358e7530e 100644
--- a/test/api-routes-test.ts
+++ b/test/api-routes-test.ts
@@ -131,6 +131,12 @@ test.describe("api routes", () => {
           "src/routes/api/[param]/index.js": js`
             import { json } from "solid-start/server";
             export let GET = ({ params }) => json(params);
+          `,
+          "src/routes/method-not-allowed.jsx": js`
+            export default function Page() { return <div>page</div>; }
+          `,
+          "src/routes/api/method-not-allowed.js": js`
+            export function POST () { return new Response(); }
           `
         }
       });
@@ -280,5 +286,23 @@ test.describe("api routes", () => {
       expect(res.headers.get("content-type")).toEqual("application/json; charset=utf-8");
       expect(await res.json()).toEqual({ static: true });
     });
+
+    test("should return 405 for undefined handlers on route with only a default export", async () => {
+      let res = await fixture.requestDocument("/method-not-allowed", { method: "GET" });
+      expect(res.status).toEqual(200);
+      ["POST", "PUT", "PATCH", "DELETE"].forEach(async method => {
+        res = await fixture.requestDocument("/method-not-allowed", { method });
+        expect(res.status).toEqual(405);
+      })
+    });
+
+    test("should return 405 for undefined handlers on route with only a POST export", async () => {
+      let res = await fixture.requestDocument("/api/method-not-allowed", { method: "POST" });
+      expect(res.status).toEqual(200);
+      ["GET", "PUT", "PATCH", "DELETE"].forEach(async method => {
+        res = await fixture.requestDocument("/api/method-not-allowed", { method });
+        expect(res.status).toEqual(405);
+      });
+    });
   }
 });