diff --git a/src/Form/PageSpecificClassSettingsForm.php b/src/Form/PageSpecificClassSettingsForm.php
index 1cf33b039d447d8e8abc9122265242a98801338b..79196ea468161e9c1dac34bb70c74ceaaa58b8fe 100644
--- a/src/Form/PageSpecificClassSettingsForm.php
+++ b/src/Form/PageSpecificClassSettingsForm.php
@@ -68,7 +68,7 @@ class PageSpecificClassSettingsForm extends ConfigFormBase {
   public function validateForm(array &$form, FormStateInterface $form_state) {
     $url_with_class = $form_state->getValue('url_with_class');
     if (!empty($url_with_class)) {
-      $enteredArr = explode(PHP_EOL, $url_with_class);
+      $enteredArr = explode(PHP_EOL, (string) $url_with_class);
       foreach ($enteredArr as $values) {
         $urlWithClassArr = explode("|", $values);
         $url = $urlWithClassArr[0];