diff --git a/library/Notifications/Web/Form/ContactForm.php b/library/Notifications/Web/Form/ContactForm.php
index bd2037fde..980a30231 100644
--- a/library/Notifications/Web/Form/ContactForm.php
+++ b/library/Notifications/Web/Form/ContactForm.php
@@ -16,6 +16,7 @@
 use ipl\Stdlib\Filter;
 use ipl\Validator\CallbackValidator;
 use ipl\Validator\EmailAddressValidator;
+use ipl\Validator\StringLengthValidator;
 use ipl\Web\Common\CsrfCounterMeasure;
 use ipl\Web\Compat\CompatForm;
 
@@ -95,20 +96,23 @@ protected function assemble()
             'username',
             [
                 'label' => $this->translate('Username'),
-                'validators' => [new CallbackValidator(function ($value, $validator) {
-                    $contact = Contact::on($this->db)->filter(Filter::equal('username', $value));
-                    if ($this->contactId) {
-                        $contact->filter(Filter::unequal('id', $this->contactId));
-                    }
-
-                    if ($contact->first() !== null) {
-                        $validator->addMessage($this->translate('A contact with the same username already exists.'));
-
-                        return false;
-                    }
-
-                    return true;
-                })]
+                'validators' => [
+                    new StringLengthValidator(['max' => 254]),
+                    new CallbackValidator(function ($value, $validator) {
+                        $contact = Contact::on($this->db)->filter(Filter::equal('username', $value));
+                        if ($this->contactId) {
+                            $contact->filter(Filter::unequal('id', $this->contactId));
+                        }
+
+                        if ($contact->first() !== null) {
+                            $validator->addMessage($this->translate('A contact with the same username already exists.'));
+
+                            return false;
+                        }
+
+                        return true;
+                    })
+                ]
             ]
         )->addElement(
             'select',