diff --git a/lib/UserBackend.php b/lib/UserBackend.php
index f89758141..de3bb415f 100644
--- a/lib/UserBackend.php
+++ b/lib/UserBackend.php
@@ -233,7 +233,7 @@ public function getDisplayNames($search = '', $limit = null, $offset = null): ar
 				->orWhere($query->expr()->iLike('displayname', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
 				->orWhere($query->expr()->iLike('configvalue', $query->createPositionalParameter('%' . $this->dbConn->escapeLikeParameter($search) . '%')))
 				->orderBy($query->func()->lower('displayname'), 'ASC')
-				->orderBy('uid_lower', 'ASC')
+				->addOrderBy('uid_lower', 'ASC')
 				->setMaxResults($limit)
 				->setFirstResult($offset);
 		}
diff --git a/tests/unit/UserBackendTest.php b/tests/unit/UserBackendTest.php
index 4cdaa5400..c27b94cb3 100644
--- a/tests/unit/UserBackendTest.php
+++ b/tests/unit/UserBackendTest.php
@@ -126,4 +126,17 @@ public function testOutdatedPasswordHashIsUpgradedOnEmailLogin(): void {
 
 		$this->assertNotEquals($legacyHash, $this->backend->getPasswordHash($uid));
 	}
+
+	/**
+	 * Searching orders by display name first, which also decides which
+	 * guests a limited search returns.
+	 */
+	public function testSearchIsOrderedByDisplayName(): void {
+		$this->backend->createUser('aaa@example.tld', 'bar');
+		$this->backend->setDisplayName('aaa@example.tld', 'Zoe');
+		$this->backend->createUser('zzz@example.tld', 'bar');
+		$this->backend->setDisplayName('zzz@example.tld', 'Alice');
+
+		$this->assertEquals(['Alice', 'Zoe'], array_values($this->backend->getDisplayNames('example.tld')));
+	}
 }