diff --git a/core/modules/editor/editor.module b/core/modules/editor/editor.module
index dccf823..a5091e8 100644
--- a/core/modules/editor/editor.module
+++ b/core/modules/editor/editor.module
@@ -570,6 +570,9 @@ function _editor_get_file_uuids_by_field(EntityInterface $entity) {
 /**
  * Determines the formatted text fields on an entity.
  *
+ * A field type is considered to provide formatted text if its class is a
+ * subclass of Drupal\text\Plugin\Field\FieldType\TextItemBase.
+ *
  * @param \Drupal\Core\Entity\FieldableEntityInterface $entity
  *   An entity whose fields to analyze.
  *
@@ -583,8 +586,12 @@ function _editor_get_formatted_text_fields(FieldableEntityInterface $entity) {
   }
 
   // Only return formatted text fields.
-  return array_keys(array_filter($field_definitions, function (FieldDefinitionInterface $definition) {
-    return in_array($definition->getType(), ['text', 'text_long', 'text_with_summary'], TRUE);
+  // @todo: improve as part of https://www.drupal.org/node/2732429
+  $field_type_manager = \Drupal::service('plugin.manager.field.field_type');
+  return array_keys(array_filter($field_definitions, function (FieldDefinitionInterface $definition) use ($field_type_manager) {
+    $type = $definition->getType();
+    $plugin_class = $field_type_manager->getPluginClass($type);
+    return is_subclass_of($plugin_class, 'Drupal\text\Plugin\Field\FieldType\TextItemBase');
   }));
 }
 
diff --git a/core/modules/editor/tests/modules/src/Plugin/Field/FieldType/EditorTestTextLongItem.php b/core/modules/editor/tests/modules/src/Plugin/Field/FieldType/EditorTestTextLongItem.php
new file mode 100644
index 0000000..607ab29
--- /dev/null
+++ b/core/modules/editor/tests/modules/src/Plugin/Field/FieldType/EditorTestTextLongItem.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Drupal\editor_test\Plugin\Field\FieldType;
+
+use Drupal\text\Plugin\Field\FieldType\TextLongItem;
+
+/**
+ * Plugin implementation of the 'text_long' field type.
+ *
+ * @FieldType(
+ *   id = "editor_test_text_long",
+ *   label = @Translation("Filter test text (formatted, long)"),
+ *   description = @Translation("This field stores a long text with a text format."),
+ *   category = @Translation("Text"),
+ *   default_widget = "text_textarea",
+ *   default_formatter = "text_default"
+ * )
+ */
+class EditorTestTextLongItem extends TextLongItem {
+
+}
diff --git a/core/modules/editor/tests/src/Kernel/EditorFileUsageTest.php b/core/modules/editor/tests/src/Kernel/EditorFileUsageTest.php
index aac665d..20b65d2 100644
--- a/core/modules/editor/tests/src/Kernel/EditorFileUsageTest.php
+++ b/core/modules/editor/tests/src/Kernel/EditorFileUsageTest.php
@@ -7,6 +7,7 @@
 use Drupal\node\Entity\Node;
 use Drupal\node\Entity\NodeType;
 use Drupal\file\Entity\File;
+use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\filter\Entity\FilterFormat;
@@ -57,6 +58,18 @@ protected function setUp() {
     $type = NodeType::create(['type' => 'page', 'name' => 'page']);
     $type->save();
     node_add_body_field($type);
+    FieldStorageConfig::create([
+      'field_name' => 'description',
+      'entity_type' => 'node',
+      'type' => 'editor_test_text_long',
+      'cardinality' => FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED,
+    ])->save();
+    FieldConfig::create([
+      'field_name' => 'description',
+      'entity_type' => 'node',
+      'bundle' => 'page',
+      'label' => 'Description',
+    ])->save();
   }
 
   /**
@@ -83,6 +96,7 @@ public function testEditorEntityHooks() {
     }
 
     $body = [];
+    $description = [];
     foreach ($image_entities as $key => $image_entity) {
       // Don't be rude, say hello.
       $body_value = '<p>Hello, world!</p>';
@@ -99,6 +113,10 @@ public function testEditorEntityHooks() {
         'value' => $body_value,
         'format' => 'filtered_html',
       ];
+      $description[] = [
+        'value' => 'something',
+        'format' => 'filtered_html',
+      ];
     }
 
     // Test editor_entity_insert(): increment.
@@ -107,6 +125,7 @@ public function testEditorEntityHooks() {
       'type' => 'page',
       'title' => 'test',
       'body' => $body,
+      'description' => $description,
       'uid' => 1,
     ]);
     $node->save();
@@ -199,6 +218,28 @@ public function testEditorEntityHooks() {
       $this->assertIdentical(['editor' => ['node' => [1 => '2']]], $file_usage->listUsage($image_entity), 'The image ' . $image_paths[$key] . ' has 2 usages.');
     }
 
+    // Empty out the body and summary. The number of usages should decrease by
+    // one.
+    foreach ($original_values as $key => $original_value) {
+      $node->body[$key]->value = '';
+      $node->body[$key]->summary = '';
+    }
+    $node->save();
+    foreach ($image_entities as $key => $image_entity) {
+      $this->assertIdentical(['editor' => ['node' => [1 => '1']]], $file_usage->listUsage($image_entity), 'The image ' . $image_paths[$key] . ' has 1 usage.');
+    }
+
+    // Set the field of a custom field type that is a subclass of
+    // Drupal\text\Plugin\Field\FieldType\TextItemBase. The number of usages
+    // should increase by one.
+    foreach ($original_values as $key => $original_value) {
+      $node->description[$key]->value = $original_value;
+    }
+    $node->save();
+    foreach ($image_entities as $key => $image_entity) {
+      $this->assertIdentical(['editor' => ['node' => [1 => '2']]], $file_usage->listUsage($image_entity), 'The image ' . $image_paths[$key] . ' has 2 usages.');
+    }
+
     // Test editor_entity_delete().
     $node->delete();
     foreach ($image_entities as $key => $image_entity) {