diff --git a/core/modules/migrate/src/Plugin/migrate/destination/Config.php b/core/modules/migrate/src/Plugin/migrate/destination/Config.php
index 51e1b99..a7b5de2 100644
--- a/core/modules/migrate/src/Plugin/migrate/destination/Config.php
+++ b/core/modules/migrate/src/Plugin/migrate/destination/Config.php
@@ -70,7 +70,7 @@ public static function create(ContainerInterface $container, array $configuratio
   public function import(Row $row, array $old_destination_id_values = array()) {
     foreach ($row->getRawDestination() as $key => $value) {
       if (isset($value) || !empty($this->configuration['store null'])) {
-        $this->config->set(str_replace(Row::DESTINATION_PROPERTY_SEPARATOR, '.', $key), $value);
+        $this->config->set(str_replace(Row::PROPERTY_SEPARATOR, '.', $key), $value);
       }
     }
     $this->config->save();
diff --git a/core/modules/migrate/src/Plugin/migrate/destination/EntityConfigBase.php b/core/modules/migrate/src/Plugin/migrate/destination/EntityConfigBase.php
index 5e3c143..3205898 100644
--- a/core/modules/migrate/src/Plugin/migrate/destination/EntityConfigBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/destination/EntityConfigBase.php
@@ -75,7 +75,7 @@ public function getIds() {
    */
   protected function updateEntity(EntityInterface $entity, Row $row) {
     foreach ($row->getRawDestination() as $property => $value) {
-      $this->updateEntityProperty($entity, explode(Row::DESTINATION_PROPERTY_SEPARATOR, $property), $value);
+      $this->updateEntityProperty($entity, explode(Row::PROPERTY_SEPARATOR, $property), $value);
     }
   }
 
diff --git a/core/modules/migrate/src/Row.php b/core/modules/migrate/src/Row.php
index d2c2d96..b96f1ac 100644
--- a/core/modules/migrate/src/Row.php
+++ b/core/modules/migrate/src/Row.php
@@ -37,9 +37,9 @@ class Row {
   protected $destination = array();
 
   /**
-   * Level separator of destination properties.
+   * Level separator of destination and source properties.
    */
-  const DESTINATION_PROPERTY_SEPARATOR = '/';
+  const PROPERTY_SEPARATOR = '/';
 
   /**
    * The mapping between source and destination identifiers.
@@ -124,7 +124,7 @@ public function getSourceIdValues() {
    *   TRUE if the source has property; FALSE otherwise.
    */
   public function hasSourceProperty($property) {
-    return NestedArray::keyExists($this->source, explode('.', $property));
+    return NestedArray::keyExists($this->source, explode(static::PROPERTY_SEPARATOR, $property));
   }
 
   /**
@@ -137,7 +137,7 @@ public function hasSourceProperty($property) {
    *   The found returned property or NULL if not found.
    */
   public function getSourceProperty($property) {
-    $return = NestedArray::getValue($this->source, explode('.', $property), $key_exists);
+    $return = NestedArray::getValue($this->source, explode(static::PROPERTY_SEPARATOR, $property), $key_exists);
     if ($key_exists) {
       return $return;
     }
@@ -170,7 +170,7 @@ public function setSourceProperty($property, $data) {
       throw new \Exception("The source is frozen and can't be changed any more");
     }
     else {
-      NestedArray::setValue($this->source, explode('.', $property), $data, TRUE);
+      NestedArray::setValue($this->source, explode(static::PROPERTY_SEPARATOR, $property), $data, TRUE);
     }
   }
 
@@ -191,7 +191,7 @@ public function freezeSource() {
    *   TRUE if the destination property exists.
    */
   public function hasDestinationProperty($property) {
-    return NestedArray::keyExists($this->destination, explode($this::DESTINATION_PROPERTY_SEPARATOR, $property));
+    return NestedArray::keyExists($this->destination, explode($this::PROPERTY_SEPARATOR, $property));
   }
 
   /**
@@ -204,7 +204,7 @@ public function hasDestinationProperty($property) {
    */
   public function setDestinationProperty($property, $value) {
     $this->rawDestination[$property] = $value;
-    NestedArray::setValue($this->destination, explode($this::DESTINATION_PROPERTY_SEPARATOR, $property), $value, TRUE);
+    NestedArray::setValue($this->destination, explode($this::PROPERTY_SEPARATOR, $property), $value, TRUE);
   }
 
   /**
@@ -220,10 +220,10 @@ public function getDestination() {
   /**
    * Returns the raw destination. Rarely necessary.
    *
-   * For example calling setDestination('foo:bar', 'baz') results in
+   * For example calling setDestination('foo/bar', 'baz') results in
    * @code
    * $this->destination['foo']['bar'] = 'baz';
-   * $this->rawDestination['foo.bar'] = 'baz';
+   * $this->rawDestination['foo/bar'] = 'baz';
    * @encode
    *
    * @return array
@@ -243,7 +243,7 @@ public function getRawDestination() {
    *   The destination value.
    */
   public function getDestinationProperty($property) {
-    return NestedArray::getValue($this->destination, explode($this::DESTINATION_PROPERTY_SEPARATOR, $property));
+    return NestedArray::getValue($this->destination, explode($this::PROPERTY_SEPARATOR, $property));
   }
 
   /**
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment.yml
index ea8f2fe..0ccec0f 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment.yml
@@ -19,9 +19,9 @@ process:
     plugin: migration
     migration: d6_node
     source: nid
-  entity_type: constants.entity_type
-  field_name: constants.field_name
-  comment_type: constants.comment_type
+  entity_type: 'constants/entity_type'
+  field_name: 'constants/field_name'
+  comment_type: 'constants/comment_type'
   subject: subject
   uid:
     -
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_display.yml
index a99f84e..f9c4743 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_display.yml
@@ -11,10 +11,10 @@ source:
       type: comment_default
       weight: 20
 process:
-  entity_type: constants.entity_type
-  field_name: constants.field_name
-  view_mode: constants.view_mode
-  options: constants.options
+  entity_type: 'constants/entity_type'
+  field_name: 'constants/field_name'
+  view_mode: 'constants/view_mode'
+  options: 'constants/options'
 
   bundle: node_type
 destination:
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_form_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_form_display.yml
index d82c812..a845b84 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_form_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_entity_form_display.yml
@@ -10,10 +10,10 @@ source:
       type: comment_default
       weight: 20
 process:
-  entity_type: constants.entity_type
-  field_name: constants.field_name
-  form_mode: constants.form_mode
-  options: constants.options
+  entity_type: 'constants/entity_type'
+  field_name: 'constants/field_name'
+  form_mode: 'constants/form_mode'
+  options: 'constants/options'
 
   bundle: node_type
 destination:
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field.yml
index 2a5ccc4..175ac8c 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field.yml
@@ -10,10 +10,10 @@ source:
     settings:
       content_type: comment
 process:
-  entity_type: constants.entity_type
-  id: constants.id
-  name: constants.name
-  type: constants.type
-  settings: constants.settings
+  entity_type: 'constants/entity_type'
+  id: 'constants/id'
+  name: 'constants/name'
+  type: 'constants/type'
+  settings: 'constants/settings'
 destination:
   plugin: entity:field_config
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field_instance.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field_instance.yml
index a39d870..6d9b14c 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field_instance.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_field_instance.yml
@@ -8,10 +8,10 @@ source:
     label: Comment settings
     required: true
 process:
-  entity_type: constants.entity_type
-  field_name: constants.field_name
-  label: constants.label
-  required: constants.required
+  entity_type: 'constants/entity_type'
+  field_name: 'constants/field_name'
+  label: 'constants/label'
+  required: 'constants/required'
 
   bundle: node_type
   'default_value/0/status': comment
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_type.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_type.yml
index 6bd490b..26cef49 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_type.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_comment_type.yml
@@ -17,9 +17,9 @@ source:
     label: comment
     description: comment
 process:
-  target_entity_type_id: constants.entity_type
-  id: constants.id
-  label: constants.label
-  description: constants.description
+  target_entity_type_id: 'constants/entity_type'
+  id: 'constants/id'
+  label: 'constants/label'
+  description: 'constants/description'
 destination:
   plugin: entity:comment_type
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_custom_block.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_custom_block.yml
index 2ff0501..bbaa2fb 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_custom_block.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_custom_block.yml
@@ -6,7 +6,7 @@ source:
     type: basic
 process:
   id: bid
-  type: constants.type
+  type: 'constants/type'
   info: info
   'body/format':
     plugin: migration
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field.yml
index 9ce7638..d68e2c7 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field.yml
@@ -6,9 +6,9 @@ source:
     entity_type: node
     langcode: und
 process:
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   status: active
-  langcode: constants.langcode
+  langcode: 'constants/langcode'
   name: field_name
   type:
     -
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_formatter_settings.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_formatter_settings.yml
index 9409eff..a47ca6d 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_formatter_settings.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_formatter_settings.yml
@@ -21,7 +21,7 @@ process:
         - 1
     -
       plugin: skip_row_on_empty
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   bundle: type_name
   view_mode:
     -
@@ -291,7 +291,7 @@ process:
             trim_length: 600
     -
       plugin: field_formatter_settings_defaults
-  "options/third_party_settings": constants.third_party_settings
+  "options/third_party_settings": 'constants/third_party_settings'
 
 destination:
   plugin: component_entity_display
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml
index 74e3536..9c34a72 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance.yml
@@ -20,7 +20,7 @@ process:
         - 1
     -
       plugin: skip_row_on_empty
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   field_name: field_name
   bundle: type_name
   label: label
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance_widget_settings.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance_widget_settings.yml
index 833876a..eebe967 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance_widget_settings.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_field_instance_widget_settings.yml
@@ -23,9 +23,9 @@ process:
     -
       plugin: skip_row_on_empty
   bundle: type_name
-  form_mode: constants.form_mode
+  form_mode: 'constants/form_mode'
   field_name: field_name
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   'options/weight': weight
   'options/type':
     type:
@@ -51,7 +51,7 @@ process:
       source:
         - widget_type
         - widget_settings
-  'options/third_party_settings': constants.third_party_settings
+  'options/third_party_settings': 'constants/third_party_settings'
 
 destination:
   plugin: component_entity_form_display
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_node_type.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_node_type.yml
index fe91810..0681135 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_node_type.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_node_type.yml
@@ -12,7 +12,7 @@ process:
   description: description
   help: help
   title_label: title_label
-  preview: constants.preview
+  preview: 'constants/preview'
   submitted: submitted
   options: options
   create_body: has_body
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_search_page.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_search_page.yml
index 2bddcb5..38977e8 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_search_page.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_search_page.yml
@@ -14,9 +14,9 @@ source:
     path: node
     plugin: node_search
 process:
-  id: constants.id
-  path: constants.path
-  plugin: constants.plugin
+  id: 'constants/id'
+  path: 'constants/path'
+  plugin: 'constants/plugin'
   'configuration/rankings':
     plugin: d6_search_configuration_rankings
 destination:
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_display.yml
index 0d625d1..b29a1ca 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_display.yml
@@ -11,12 +11,12 @@ source:
       label: hidden
       settings: {}
 process:
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   bundle: node_type
-  view_mode: constants.view_mode
-  field_name: constants.name
-  type: constants.type
-  options: constants.options
+  view_mode: 'constants/view_mode'
+  field_name: 'constants/name'
+  type: 'constants/type'
+  options: 'constants/options'
   'options/type': @type
 destination:
   plugin: component_entity_display
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_form_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_form_display.yml
index c4a1662..1a098ae 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_form_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_entity_form_display.yml
@@ -13,12 +13,12 @@ source:
       settings:
         progress_indicator: throbber
 process:
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   bundle: node_type
-  field_name: constants.name
-  form_mode: constants.form_mode
-  type: constants.type
-  options: constants.options
+  field_name: 'constants/name'
+  form_mode: 'constants/form_mode'
+  type: 'constants/type'
+  options: 'constants/options'
   'options/type': @type
 destination:
   plugin: component_entity_form_display
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field.yml
index 0cf1336..f055f95 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field.yml
@@ -12,10 +12,10 @@ source:
     cardinality: -1
     display_field: true
 process:
-  entity_type: constants.entity_type
-  name: constants.name
-  type: constants.type
-  cardinality: constants.cardinality
-  'settings/display_field': constants.display_field
+  entity_type: 'constants/entity_type'
+  name: 'constants/name'
+  type: 'constants/type'
+  cardinality: 'constants/cardinality'
+  'settings/display_field': 'constants/display_field'
 destination:
   plugin: entity:field_config
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field_instance.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field_instance.yml
index d406e41..5aa5179 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field_instance.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_upload_field_instance.yml
@@ -8,10 +8,10 @@ source:
     settings:
       description_field: 1
 process:
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   bundle: node_type
-  field_name: constants.name
-  settings: constants.settings
+  field_name: 'constants/name'
+  settings: 'constants/settings'
   'settings/file_extensions': file_extensions
   'settings/max_filesize': max_filesize
 destination:
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_display.yml
index c2b6633..adfdd83 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_display.yml
@@ -14,12 +14,12 @@ source:
         image_style: ''
         image_link: content
 process:
-  entity_type: constants.entity_type
-  bundle: constants.bundle
-  view_mode: constants.view_mode
-  field_name: constants.name
-  type: constants.type
-  options: constants.options
+  entity_type: 'constants/entity_type'
+  bundle: 'constants/bundle'
+  view_mode: 'constants/view_mode'
+  field_name: 'constants/name'
+  type: 'constants/type'
+  options: 'constants/options'
   'options/type': @type
 destination:
   plugin: component_entity_display
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_form_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_form_display.yml
index 53e5e2c..39c2a81 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_form_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_entity_form_display.yml
@@ -14,12 +14,12 @@ source:
         progress_indicator: throbber
         preview_image_style: thumbnail
 process:
-  entity_type: constants.entity_type
-  bundle: constants.bundle
-  field_name: constants.name
-  form_mode: constants.form_mode
-  type: constants.type
-  options: constants.options
+  entity_type: 'constants/entity_type'
+  bundle: 'constants/bundle'
+  field_name: 'constants/name'
+  form_mode: 'constants/form_mode'
+  type: 'constants/type'
+  options: 'constants/options'
   'options/type': @type
 destination:
   plugin: component_entity_form_display
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field.yml
index ed53dd1..5a4a992 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field.yml
@@ -10,9 +10,9 @@ source:
     name: user_picture
     cardinality: 1
 process:
-  entity_type: constants.entity_type
-  name: constants.name
-  type: constants.type
-  cardinality: constants.cardinality
+  entity_type: 'constants/entity_type'
+  name: 'constants/name'
+  type: 'constants/type'
+  cardinality: 'constants/cardinality'
 destination:
   plugin: entity:field_config
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field_instance.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field_instance.yml
index 876ae01..74b4838 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field_instance.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_field_instance.yml
@@ -14,10 +14,10 @@ source:
       alt_field_required: false
       title_field_required: false
 process:
-  entity_type: constants.entity_type
-  bundle: constants.bundle
-  field_name: constants.name
-  settings: constants.settings
+  entity_type: 'constants/entity_type'
+  bundle: 'constants/bundle'
+  field_name: 'constants/name'
+  settings: 'constants/settings'
   'settings/file_directory': file_directory
   'settings/max_filesize': max_filesize
   'settings/max_resolution': max_resolution
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_file.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_file.yml
index b97950b..21c53e1 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_file.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_picture_file.yml
@@ -11,7 +11,7 @@ process:
     source:
       - picture
       - file_directory_path
-      - constants.is_public
+      - 'constants/is_public'
 destination:
   plugin: entity:file
   source_path_property: picture
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_display.yml
index d608722..57146a5 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_display.yml
@@ -10,9 +10,9 @@ source:
       label: hidden
       settings: {}
 process:
-  entity_type: constants.entity_type
-  bundle: constants.bundle
-  view_mode: constants.view_mode
+  entity_type: 'constants/entity_type'
+  bundle: 'constants/bundle'
+  view_mode: 'constants/view_mode'
   field_name: name
   type:
     plugin: static_map
@@ -25,7 +25,7 @@ process:
       textfield: text_default
       textarea: text_default
       url: link_default
-  options: constants.options
+  options: 'constants/options'
   'options/type': @type
   hidden:
     plugin: static_map
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_form_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_form_display.yml
index 144b081..0ace57a 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_form_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_entity_form_display.yml
@@ -10,10 +10,10 @@ source:
     options:
       label: hidden
 process:
-  entity_type: constants.entity_type
-  bundle: constants.bundle
+  entity_type: 'constants/entity_type'
+  bundle: 'constants/bundle'
   field_name: name
-  form_mode: constants.form_mode
+  form_mode: 'constants/form_mode'
   type:
     plugin: static_map
     source: type
@@ -25,13 +25,13 @@ process:
       textfield: text_textfield
       textarea: text_textarea
       url: link_default
-  options: constants.options
+  options: 'constants/options'
   'options/type': @type
   'options/settings':
     plugin: field_instance_widget_settings
     source:
       - @type
-      - constants.empty # we don't have any settings.
+      - 'constants/empty' # we don't have any settings.
   'options/settings/display_label':  # Single on/off checkboxes need to have display_label = true otherwise their label doesn't show.
     plugin: static_map
     default_value: false
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field.yml
index 183a265..a075708 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field.yml
@@ -5,7 +5,7 @@ source:
   constants:
     entity_type: user
 process:
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   name: name
   type:
     plugin: static_map
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field_instance.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field_instance.yml
index 34a77ac..443d0ec 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field_instance.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_user_profile_field_instance.yml
@@ -6,8 +6,8 @@ source:
     entity_type: user
     bundle: user
 process:
-  entity_type: constants.entity_type
-  bundle: constants.bundle
+  entity_type: 'constants/entity_type'
+  bundle: 'constants/bundle'
   label: title
   description: explanation
   field_name: name
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_view_modes.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_view_modes.yml
index 3bc9131..a2474c2 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_view_modes.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_view_modes.yml
@@ -31,8 +31,8 @@ process:
       5: "Print"
       teaser: "Teaser"
       full: "Full"
-  targetEntityType: constants.targetEntityType
-  status: constants.status
+  targetEntityType: 'constants/targetEntityType'
+  status: 'constants/status'
 
 destination:
   plugin: entity:view_mode
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_display.yml
index a81af39..65d1fa0 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_display.yml
@@ -11,9 +11,9 @@ source:
       weight: 20
 
 process:
-  entity_type: constants.entity_type
-  view_mode: constants.view_mode
-  options: constants.options
+  entity_type: 'constants/entity_type'
+  view_mode: 'constants/view_mode'
+  options: 'constants/options'
   bundle: type
   field_name:
     plugin: migration
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_form_display.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_form_display.yml
index 249b3b3..945f89d 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_form_display.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_entity_form_display.yml
@@ -9,9 +9,9 @@ source:
       type: options_select
       weight: 20
 process:
-  entity_type: constants.entity_type
-  form_mode: constants.form_mode
-  options: constants.options
+  entity_type: 'constants/entity_type'
+  form_mode: 'constants/form_mode'
+  options: 'constants/options'
   bundle: type
   field_name:
     plugin: migration
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field.yml
index 9c2cb88..93cacd9 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field.yml
@@ -8,15 +8,15 @@ source:
     parent: 0
     cardinality: -1
 process:
-  entity_type: constants.entity_type
-  type: constants.type
+  entity_type: 'constants/entity_type'
+  type: 'constants/type'
   name:
     plugin: migration
     migration: d6_taxonomy_vocabulary
     source: vid
   'settings/allowed_values/0/vocabulary': @name
-  'settings/allowed_values/0/parent': constants.parent
-  cardinality: constants.cardinality
+  'settings/allowed_values/0/parent': 'constants/parent'
+  cardinality: 'constants/cardinality'
 destination:
   plugin: entity:field_config
 migration_dependencies:
diff --git a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field_instance.yml b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field_instance.yml
index c7fc497..6427f84 100644
--- a/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field_instance.yml
+++ b/core/modules/migrate_drupal/config/install/migrate.migration.d6_vocabulary_field_instance.yml
@@ -6,7 +6,7 @@ source:
     entity_type: node
     parent: 0
 process:
-  entity_type: constants.entity_type
+  entity_type: 'constants/entity_type'
   bundle: type
   field_name:
     plugin: migration