diff --git a/api/source/errors.ts b/api/source/errors.ts
new file mode 100644
index 000000000..bdf9205dc
--- /dev/null
+++ b/api/source/errors.ts
@@ -0,0 +1,26 @@
+import { Middleware } from 'koa'
+
+type JsonError = { status: number; body: string; message: string }
+
+const isJsonError = (err: unknown): err is JsonError =>
+	!!err &&
+	typeof err === 'object' &&
+	'message' in err &&
+	'status' in err &&
+	'body' in err &&
+	(err as { status: unknown }).status === 400 &&
+	typeof (err as { body: unknown }).body === 'string' &&
+	typeof (err as { message: unknown }).message === 'string'
+
+export const catchErrors = (): Middleware => async (ctx, next) => {
+	try {
+		await next()
+	} catch (error) {
+		if (isJsonError(error)) {
+			ctx.status = error.status
+			ctx.body = error.message
+		} else {
+			throw error
+		}
+	}
+}
diff --git a/api/source/index.ts b/api/source/index.ts
index e11c37fe4..fe080fac3 100644
--- a/api/source/index.ts
+++ b/api/source/index.ts
@@ -4,6 +4,7 @@ import { koaMiddleware as publicodesAPI } from '@publicodes/api'
 import Koa from 'koa'
 import rules from 'modele-social'
 import Engine from 'publicodes'
+import { catchErrors } from './errors.js'
 import openapi from './openapi.json' assert { type: 'json' }
 import { docRoutes } from './route/doc.js'
 import { openapiRoutes } from './route/openapi.js'
@@ -29,6 +30,8 @@ if (process.env.NODE_ENV === 'production') {
 	})
 }
 
+app.use(catchErrors())
+
 app.use(cors())
 
 const apiRoutes = publicodesAPI(new Engine(rules))