diff --git a/views/sheets/edit_assignment.php b/views/sheets/edit_assignment.php
index 0133191acf47748ef7625cb137e68a713dafac2e..a93afb49cb39522fd91d6050dfad424f0fe3721a 100644
--- a/views/sheets/edit_assignment.php
+++ b/views/sheets/edit_assignment.php
@@ -58,7 +58,7 @@
 
         <label id="exam_length" class="practice-hidden selftest-hidden">
             <span class="required"><?= _vips('Dauer in Minuten') ?></span>
-            <input type="number" name="exam_length" value="<?= htmlReady($assignment->options['duration']) ?>" <?= $disabled ?> data-secure required>
+            <input type="number" name="exam_length" min="0" max="99999" value="<?= htmlReady($assignment->options['duration']) ?>" <?= $disabled ?> data-secure required>
         </label>
 
         <input id="options-toggle" type="checkbox" value="on" <?= $assignment_id ? '' : 'checked' ?>>