diff --git a/permissions_by_term.module b/permissions_by_term.module
index 500c94f..42f058a 100644
--- a/permissions_by_term.module
+++ b/permissions_by_term.module
@@ -308,7 +308,9 @@ function permissions_by_term_user_form_submit(array &$form, FormStateInterface $
 
   // Rebuild permissions for nodes if needed.
   $origTerms = $form['access']['terms']['#default_value'] ?? [];
-  $newTerms = $form_state->getValue('terms');
+  // Get new selected terms. When no term is selected, Drupal does not return
+  // an array here but an empty string, so assume an empty array in that case.
+  $newTerms = is_array($form_state->getValue('terms')) ? $form_state->getValue('terms') : [];
   $changes = array_diff($origTerms, $newTerms) + array_diff($newTerms, $origTerms);
 
   if (!\Drupal::config('permissions_by_term.settings')->get('disable_node_access_records') &&