diff --git a/packages/backend/scripts/generate_api_json.js b/packages/backend/scripts/generate_api_json.js
index 59f7350845..237f63a4d3 100644
--- a/packages/backend/scripts/generate_api_json.js
+++ b/packages/backend/scripts/generate_api_json.js
@@ -3,7 +3,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import { writeFileSync } from 'node:fs';
+import { writeFileSync, existsSync } from 'node:fs';
 import { execa } from 'execa';
 
 async function main() {
@@ -14,6 +14,10 @@ async function main() {
 		});
 	}
 
+	if (!existsSync('./built')) {
+		throw new Error('`built` directory does not exist.');
+	}
+
 	/** @type {import('../src/config.js')} */
 	const { loadConfig } = await import('../src-js/config.js');