diff --git a/cdk/backend.ts b/cdk/backend.ts
index 6c9bd11..b11de4c 100644
--- a/cdk/backend.ts
+++ b/cdk/backend.ts
@@ -14,7 +14,7 @@ const packagesInLayer: string[] = [
 ]
 const pack = async (
 	id: string,
-	handler = `${id}.handler`,
+	handlerFunction = 'handler',
 ): Promise<PackedLambda> => {
 	try {
 		await mkdir(path.join(process.cwd(), 'dist', 'lambdas'), {
@@ -24,13 +24,13 @@ const pack = async (
 		// Directory exists
 	}
 	const zipFile = path.join(process.cwd(), 'dist', 'lambdas', `${id}.zip`)
-	await packLambda({
+	const { handler } = await packLambda({
 		sourceFile: path.join(process.cwd(), 'lambda', `${id}.ts`),
 		zipFile,
 	})
 	return {
 		lambdaZipFile: zipFile,
-		handler,
+		handler: handler.replace('.js', `.${handlerFunction}`),
 	}
 }
 
diff --git a/cdk/packLambda.ts b/cdk/packLambda.ts
index 259e134..23d9af4 100644
--- a/cdk/packLambda.ts
+++ b/cdk/packLambda.ts
@@ -5,6 +5,21 @@ import * as yazl from 'yazl'
 import { commonParent } from './commonParent.js'
 import { findDependencies } from './findDependencies.js'
 
+const removeCommonAncestor =
+	(parentDir: string) =>
+	(file: string): string => {
+		const p = parse(file)
+		const jsFileName = [
+			p.dir.replace(parentDir.slice(0, parentDir.length - 1), ''),
+			`${p.name}.js`,
+		]
+			.join('/')
+			// Replace leading slash
+			.replace(/^\//, '')
+
+		return jsFileName
+	}
+
 /**
  * In the bundle we only include code that's not in the layer.
  */
@@ -18,12 +33,12 @@ export const packLambda = async ({
 	zipFile: string
 	debug?: (label: string, info: string) => void
 	progress?: (label: string, info: string) => void
-}): Promise<void> => {
+}): Promise<{ handler: string }> => {
 	const lambdaFiles = [sourceFile, ...findDependencies(sourceFile)]
 
 	const zipfile = new yazl.ZipFile()
 
-	const parentDir = commonParent(lambdaFiles)
+	const stripCommon = removeCommonAncestor(commonParent(lambdaFiles))
 
 	for (const file of lambdaFiles) {
 		const compiled = (
@@ -34,15 +49,7 @@ export const packLambda = async ({
 			})
 		).code
 		debug?.(`compiled`, compiled)
-		const p = parse(file)
-		const jsFileName = [
-			p.dir.replace(parentDir.slice(0, parentDir.length - 1), ''),
-			`${p.name}.js`,
-		]
-			.join('/')
-			// Replace leading slash
-			.replace(/^\//, '')
-
+		const jsFileName = stripCommon(file)
 		zipfile.addBuffer(Buffer.from(compiled, 'utf-8'), jsFileName)
 		progress?.(`added`, jsFileName)
 	}
@@ -66,4 +73,6 @@ export const packLambda = async ({
 		zipfile.end()
 	})
 	progress?.(`written`, zipFile)
+
+	return { handler: stripCommon(sourceFile) }
 }