diff --git a/src/FieldAttributeConverter.php b/src/FieldAttributeConverter.php
index ff65cc05..8d5c0c2a 100644
--- a/src/FieldAttributeConverter.php
+++ b/src/FieldAttributeConverter.php
@@ -82,7 +82,11 @@ public function __construct(EntityFieldManagerInterface $entity_field_manager, F
    *   Prefix of the field.
    */
   protected function getFieldPrefix(): string {
-    return (string) $this->config->get('field_ui.settings')->get('field_prefix');
+    // If the Field UI module is installed, and has a specific prefix
+    // configured, use that. Otherwise, just default to using 'field_' as
+    // a prefix, which is the default that Field UI ships with.
+    $prefix = $this->config->get('field_ui.settings')->get('field_prefix') !== NULL ? $this->config->get('field_ui.settings')->get('field_prefix') : 'field_';
+    return (string) $prefix;
   }
 
   /**