diff --git a/VERSION b/VERSION
index d6182a8..ea9806d 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.3.98-beta
+0.3.99-beta
diff --git a/public/js/core.js b/public/js/core.js
index 029842c..4e8898d 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 = "0.3.98-beta";
+const VERSION = "0.3.99-beta";
 (function(){
   const tag = document.getElementById("verTag");
   tag.textContent = "v"+VERSION;
diff --git a/src/api.js b/src/api.js
index 7e4eff4..eb291fb 100644
--- a/src/api.js
+++ b/src/api.js
@@ -441,11 +441,15 @@ export default async function api(app) {
     need(req, reply, PERMISSIONS['users.manage']);
     // Ouders hebben school_id NULL en vallen daardoor buiten elke schoollijst;
     // een school ziet wél de ouders die aan haar eigen leerlingen gekoppeld zijn.
+    // Postgres eist bij SELECT DISTINCT dat elke ORDER BY-expressie letterlijk
+    // in de select-lijst staat - lower(p.username) alleen via p.* volstond niet
+    // (gaf "for SELECT DISTINCT, ORDER BY expressions must appear in select
+    // list"), dus expliciet als extra kolom toevoegen.
     const linkedParents = async (schoolId, extra = '', params = []) => (await pool.query(
-      `SELECT DISTINCT p.* FROM users p
+      `SELECT DISTINCT p.*, lower(p.username) AS sort_key FROM users p
        JOIN parent_children pc ON pc.parent_id = p.id
        JOIN users k ON k.id = pc.pupil_id
-       WHERE k.school_id = $1 ${extra} ORDER BY lower(p.username)`,
+       WHERE k.school_id = $1 ${extra} ORDER BY sort_key`,
       [schoolId, ...params])).rows;
     let rows;
     if (req.user.allRoles.includes('super')) {
diff --git a/test/parent-portal.test.js b/test/parent-portal.test.js
index 053beaa..5332404 100644
--- a/test/parent-portal.test.js
+++ b/test/parent-portal.test.js
@@ -289,7 +289,7 @@ test('afwijzen verwijdert alleen het verzoek; andere school mag niet afhandelen'
 });
 
 test('schoolbeheerder ziet gekoppelde ouders (met kindernamen) in de gebruikerslijst', async () => {
-  const { app } = await makeApp({ user: admin, respond: (sql) => {
+  const { app, calls } = await makeApp({ user: admin, respond: (sql) => {
     if (sql.startsWith('SELECT * FROM users WHERE school_id')) return { rows: [
       { id: 50, username: 'lena', role: 'pupil', school_id: 2, class_id: 5 },
     ] };
@@ -306,6 +306,13 @@ test('schoolbeheerder ziet gekoppelde ouders (met kindernamen) in de gebruikersl
   const p = res.json().users.find((u) => u.role === 'parent');
   assert.ok(p, 'ouder hoort in de schoollijst te staan');
   assert.deepEqual(p.childNames, ['Lena']);
+  // regressie: Postgres weigert "SELECT DISTINCT ... ORDER BY lower(p.username)"
+  // omdat die expressie niet letterlijk in de select-lijst staat (was stuk in
+  // productie voor elke school-gescopede gebruikerslijst) - de sort-expressie
+  // moet dus als kolom in de SELECT staan, niet alleen in de ORDER BY.
+  const linkedParentsCall = calls.find((c) => c.sql.includes('JOIN parent_children pc ON pc.parent_id = p.id'));
+  assert.match(linkedParentsCall.sql, /SELECT DISTINCT p\.\*, lower\(p\.username\) AS sort_key/);
+  assert.match(linkedParentsCall.sql, /ORDER BY sort_key/);
   await app.close();
 });