diff --git a/VERSION b/VERSION
index ea9806d..578dca3 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.3.99-beta
+0.4.0-beta
diff --git a/public/js/core.js b/public/js/core.js
index 4e8898d..bef9988 100644
--- a/public/js/core.js
+++ b/public/js/core.js
@@ -2,7 +2,7 @@
 "use strict";
 /* version — shown until /api/version resolves (or if the fetch fails, e.g. offline).
    Kept in sync by hand with the VERSION file at the repo root on every release. */
-const VERSION = "0.3.99-beta";
+const VERSION = "0.4.0-beta";
 (function(){
   const tag = document.getElementById("verTag");
   tag.textContent = "v"+VERSION;
diff --git a/src/api.js b/src/api.js
index eb291fb..260fac8 100644
--- a/src/api.js
+++ b/src/api.js
@@ -375,12 +375,20 @@ export default async function api(app) {
   });
   app.delete('/admin/classes/:id', async (req, reply) => {
     need(req, reply, PERMISSIONS['classes.manage']);
-    const r = await pool.query('SELECT * FROM classes WHERE id = $1', [req.params.id]);
-    if (!r.rows[0]) return fail(reply, 404, 'klas onbekend');
-    if (!req.user.allRoles.includes('super') && Number(r.rows[0].school_id) !== Number(req.user.school_id))
-      return fail(reply, 403, 'geen rechten');
-    await pool.query('DELETE FROM classes WHERE id = $1', [req.params.id]);
-    return { ok: true };
+    // Zelfde reden als bij het verwijderen van een gebruiker: alles in één
+    // try/catch, zodat een mislukking de echte oorzaak teruggeeft i.p.v. terug
+    // te vallen op de kale "serverfout" van de generieke handler.
+    try {
+      const r = await pool.query('SELECT * FROM classes WHERE id = $1', [req.params.id]);
+      if (!r.rows[0]) return fail(reply, 404, 'klas onbekend');
+      if (!req.user.allRoles.includes('super') && Number(r.rows[0].school_id) !== Number(req.user.school_id))
+        return fail(reply, 403, 'geen rechten');
+      await pool.query('DELETE FROM classes WHERE id = $1', [req.params.id]);
+      return { ok: true };
+    } catch (e) {
+      req.log.error({ err: e }, 'verwijderen klas mislukt');
+      return fail(reply, 409, `verwijderen mislukt: ${e.detail || e.message}`);
+    }
   });
   // groepsleiding aan klas koppelen/loskoppelen
   // Elke staf-rol (groepsleiding, schoolbeheerder, systeemmanager) kan aan
diff --git a/test/schools.test.js b/test/schools.test.js
index 45a7a06..6d10283 100644
--- a/test/schools.test.js
+++ b/test/schools.test.js
@@ -197,6 +197,27 @@ test('systeemmanager verplaatst een klas naar een andere school; losmaken kan ni
   await app.close(); await app2.close(); await app3.close();
 });
 
+test('klas verwijderen werkt en meldt bij een fout de echte reden i.p.v. kale serverfout', async () => {
+  const { app, calls } = await makeApp(superUser, null);
+  const res = await app.inject({ method: 'DELETE', url: '/api/admin/classes/100', cookies });
+  assert.equal(res.statusCode, 200, res.body);
+  assert.ok(calls.some((c) => c.sql === 'DELETE FROM classes WHERE id = $1'));
+
+  const { app: app2 } = await makeApp(superUser, null);
+  const pool2 = app2.pg;
+  const orig = pool2.query.bind(pool2);
+  pool2.query = async (sql, params) => {
+    if (sql === 'DELETE FROM classes WHERE id = $1') {
+      const e = new Error('boom'); e.detail = 'Key is still referenced from table "iets".'; throw e;
+    }
+    return orig(sql, params);
+  };
+  const res2 = await app2.inject({ method: 'DELETE', url: '/api/admin/classes/100', cookies });
+  assert.equal(res2.statusCode, 409, res2.body);
+  assert.match(res2.json().error, /still referenced/);
+  await app.close(); await app2.close();
+});
+
 test('gebruiker verwijderen ruimt eerst alle afhankelijke rijen op (geen serverfout)', async () => {
   const { app, calls } = await makeApp(superUser, { id: 9, role: 'teacher', school_id: 2, username: 'juf' });
   const res = await app.inject({ method: 'DELETE', url: '/api/admin/users/9', cookies });