diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/NumberWidget.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/NumberWidget.php
index d094984..d2ab50c 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/NumberWidget.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/NumberWidget.php
@@ -101,11 +101,18 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
     // Add prefix and suffix.
     if ($field_settings['prefix']) {
       $prefixes = explode('|', $field_settings['prefix']);
-      $element['#field_prefix'] = $this->fieldFilterXss($prefixes[0]);
+      $element['#field_prefix'] = $this->fieldFilterXss(array_shift($prefixes));
     }
     if ($field_settings['suffix']) {
       $suffixes = explode('|', $field_settings['suffix']);
-      $element['#field_suffix'] = $this->fieldFilterXss($suffixes[0]);
+      $element['#field_suffix'] = $this->fieldFilterXss(array_shift($suffixes));
+    }
+
+    // @TODO: Remove this warning once we have decent support for plural
+    // formatting of the prefix/suffix field.
+    // @see https://www.drupal.org/node/2449597
+    if (strstr($field_settings['prefix'], '|') || strstr($field_settings['suffix'], '|')) {
+      drupal_set_message($this->t('The prefix and/or suffix setting of the field "@title" contain a pipe symbol. Everything after the pipe, including the pipe itself, will be ignored.', ['@title' => $element['#title']]), 'warning');
     }
 
     return array('value' => $element);