diff --git a/.changeset/six-baboons-allow.md b/.changeset/six-baboons-allow.md
new file mode 100644
index 000000000000..e55e044e3dfd
--- /dev/null
+++ b/.changeset/six-baboons-allow.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/vercel': patch
+---
+
+Fix build error when passing `includeFiles`
diff --git a/packages/integrations/vercel/src/serverless/adapter.ts b/packages/integrations/vercel/src/serverless/adapter.ts
index e44aa3f0796d..592f3618ff6d 100644
--- a/packages/integrations/vercel/src/serverless/adapter.ts
+++ b/packages/integrations/vercel/src/serverless/adapter.ts
@@ -47,6 +47,8 @@ export default function vercelServerless({
 	let buildTempFolder: URL;
 	let serverEntry: string;
 	let _entryPoints: Map<RouteData, URL>;
+	// Extra files to be merged with `includeFiles` during build
+	const extraFilesToInclude: URL[] = [];
 
 	async function createFunctionFolder(funcName: string, entry: URL, inc: URL[]) {
 		const functionFolder = new URL(`./functions/${funcName}.func/`, _config.outDir);
@@ -74,8 +76,6 @@ export default function vercelServerless({
 		});
 	}
 
-	const filesToInclude = includeFiles?.map((file) => new URL(file, _config.root)) || [];
-
 	return {
 		name: PACKAGE_NAME,
 		hooks: {
@@ -130,7 +130,7 @@ export default function vercelServerless({
 						vercelEdgeMiddlewareHandlerPath
 					);
 					// let's tell the adapter that we need to save this file
-					filesToInclude.push(bundledMiddlewarePath);
+					extraFilesToInclude.push(bundledMiddlewarePath);
 				}
 			},
 
@@ -140,7 +140,7 @@ export default function vercelServerless({
 					const mergeGlobbedIncludes = (globPattern: unknown) => {
 						if (typeof globPattern === 'string') {
 							const entries = glob.sync(globPattern).map((p) => pathToFileURL(p));
-							filesToInclude.push(...entries);
+							extraFilesToInclude.push(...entries);
 						} else if (Array.isArray(globPattern)) {
 							for (const pattern of globPattern) {
 								mergeGlobbedIncludes(pattern);
@@ -152,6 +152,8 @@ export default function vercelServerless({
 				}
 
 				const routeDefinitions: { src: string; dest: string }[] = [];
+				const filesToInclude = includeFiles?.map((file) => new URL(file, _config.root)) || [];
+				filesToInclude.push(...extraFilesToInclude);
 
 				// Multiple entrypoint support
 				if (_entryPoints.size) {
diff --git a/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs b/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs
index 03228c5df506..84b96c27d409 100644
--- a/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs
+++ b/packages/integrations/vercel/test/fixtures/serverless-prerender/astro.config.mjs
@@ -2,6 +2,9 @@ import { defineConfig } from 'astro/config';
 import vercel from '@astrojs/vercel/serverless';
 
 export default defineConfig({
-	adapter: vercel(),
+	adapter: vercel({
+		// Pass some value to make sure it doesn't error out
+		includeFiles: ['included.js']
+	}),
 	output: 'server'
 });
diff --git a/packages/integrations/vercel/test/fixtures/serverless-prerender/included.js b/packages/integrations/vercel/test/fixtures/serverless-prerender/included.js
new file mode 100644
index 000000000000..4e64b2d616bf
--- /dev/null
+++ b/packages/integrations/vercel/test/fixtures/serverless-prerender/included.js
@@ -0,0 +1 @@
+'works'
\ No newline at end of file
diff --git a/packages/integrations/vercel/test/serverless-prerender.test.js b/packages/integrations/vercel/test/serverless-prerender.test.js
index 18b16534047a..292e92b69d30 100644
--- a/packages/integrations/vercel/test/serverless-prerender.test.js
+++ b/packages/integrations/vercel/test/serverless-prerender.test.js
@@ -10,12 +10,20 @@ describe('Serverless prerender', () => {
 		fixture = await loadFixture({
 			root: './fixtures/serverless-prerender/',
 		});
+		await fixture.build();
 	});
 
 	it('build successful', async () => {
-		await fixture.build();
 		expect(await fixture.readFile('../.vercel/output/static/index.html')).to.be.ok;
 	});
+
+	it('includeFiles work', async () => {
+		expect(
+			await fixture.readFile(
+				'../.vercel/output/functions/render.func/packages/integrations/vercel/test/fixtures/serverless-prerender/included.js'
+			)
+		).to.be.ok;
+	});
 });
 
 describe('Serverless hybrid rendering', () => {
@@ -28,10 +36,10 @@ describe('Serverless hybrid rendering', () => {
 			root: './fixtures/serverless-prerender/',
 			output: 'hybrid',
 		});
+		await fixture.build();
 	});
 
 	it('build successful', async () => {
-		await fixture.build();
 		expect(await fixture.readFile('../.vercel/output/static/index.html')).to.be.ok;
 	});
 });