diff -u b/core/modules/node/src/Plugin/migrate/builder/d6/Node.php b/core/modules/node/src/Plugin/migrate/builder/d6/Node.php
--- b/core/modules/node/src/Plugin/migrate/builder/d6/Node.php
+++ b/core/modules/node/src/Plugin/migrate/builder/d6/Node.php
@@ -25,7 +25,7 @@
     $fields = array();
     foreach ($this->getSourcePlugin('d6_field_instance', $template['source']) as $field) {
       $info = $field->getSource();
-      $fields[ $info['type_name'] ][ $info['field_name'] ] = $info;
+      $fields[$info['type_name']][$info['field_name']] = $info;
     }
 
     foreach ($this->getSourcePlugin('d6_node_type', $template['source']) as $row) {
diff -u b/core/modules/node/src/Plugin/migrate/builder/d7/Node.php b/core/modules/node/src/Plugin/migrate/builder/d7/Node.php
--- b/core/modules/node/src/Plugin/migrate/builder/d7/Node.php
+++ b/core/modules/node/src/Plugin/migrate/builder/d7/Node.php
@@ -25,7 +25,7 @@
     $fields = array();
     foreach ($this->getSourcePlugin('d7_field_instance', $template['source']) as $field) {
       $info = $field->getSource();
-      $fields[ $info['entity_type'] ][ $info['bundle'] ][ $info['field_name'] ] = $info;
+      $fields[$info['entity_type']][$info['bundle']][$info['field_name']] = $info;
     }
 
     foreach ($this->getSourcePlugin('d7_node_type', $template['source']) as $node_type) {