diff -u b/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/Node.php b/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/Node.php
--- b/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/Node.php
+++ b/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/Node.php
@@ -51,22 +51,25 @@
   protected $cckSchemaCorrect;
 
   /**
+   * The d6_field source plugin.
+   *
+   * @var \Drupal\migrate\Plugin\MigrateSourceInterface
+   */
+  protected $fieldSource;
+
+  /**
    * All CCK field info in the source database, keyed by node type.
    *
    * @var array
    */
-  protected $fieldInfo = [];
+  protected $fieldInfo;
 
   /**
    * {@inheritdoc}
    */
   public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, EntityManagerInterface $entity_manager, MigratePluginManager $source_plugins) {
     parent::__construct($configuration, $plugin_id, $plugin_definition, $migration, $entity_manager);
-
-    $plugin = $source_plugins->createInstance('d6_field', [], $migration);
-    foreach ($plugin as $row) {
-      $this->fieldInfo[$row->getSourceProperty('type_name')][] = $row->getSource();
-    }
+    $this->fieldSource = $source_plugins->createInstance('d6_field', [], $migration);
   }
 
   /**
@@ -246,6 +249,27 @@
   }
 
   /**
+   * Returns field and field instance definitions for all fields on a given
+   * node type.
+   *
+   * @param string $node_type
+   *   The node type to be queried.
+   *
+   * @return array
+   *   An array of field and field instance definition arrays from the source
+   *   database.
+   */
+  protected function getFieldInfo($node_type) {
+    if (!isset($this->fieldInfo)) {
+      $this->fieldInfo = [];
+      foreach ($this->fieldSource as $row) {
+        $this->fieldInfo[$row->getSourceProperty('type_name')][] = $row->getSource();
+      }
+    }
+    return @($this->fieldInfo[$node_type] ?: []);
+  }
+
+  /**
    * Determines whether a specific CCK table exists.
    */
   protected function tableExists($table) {