diff -u b/src/Form/FieldConfigCloneForm.php b/src/Form/FieldConfigCloneForm.php
--- b/src/Form/FieldConfigCloneForm.php
+++ b/src/Form/FieldConfigCloneForm.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Entity\EntityForm;
 use Drupal\Core\Entity\EntityTypeBundleInfoInterface;
+use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Entity\Query\QueryFactory;
 use Drupal\Core\Form\FormStateInterface;
@@ -162,9 +163,15 @@
   public function validateForm(array &$form, FormStateInterface $form_state) {
     parent::validateForm($form, $form_state);
 
-    if ($this->isInvalidMachineName($form_state->getValue('target_field_id'), [], $form_state)) {
+    $target_field_id = $form_state->getValue('target_field_id');
+    if ($this->isInvalidMachineName($target_field_id, [], $form_state)) {
       $form_state->setErrorByName('target_field_id', $this->t('If the current bundle is selected, a different target field must be chosen as there cannot be multiple instances of the same field in the same bundle.'));
     }
+    if (strlen($target_field_id) > EntityTypeInterface::ID_MAX_LENGTH) {
+      $form_state->setErrorByName('target_field_id', $this->t('Field machine names cannot be longer than @max_chars characters.', [
+        '@max_chars' => EntityTypeInterface::ID_MAX_LENGTH,
+      ]));
+    }
   }
 
   /**