diff --git a/core/lib/Drupal/Core/Entity/EntityFieldManagerInterface.php b/core/lib/Drupal/Core/Entity/EntityFieldManagerInterface.php
index e6a228cff5c..104e78fee46 100644
--- a/core/lib/Drupal/Core/Entity/EntityFieldManagerInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityFieldManagerInterface.php
@@ -73,7 +73,8 @@ interface EntityFieldManagerInterface {
    *   An array keyed by entity type. Each value is an array which keys are
    *   field names and value is an array with two entries:
    *   - type: The field type.
-   *   - bundles: The bundles in which the field appears.
+   *   - bundles: An associative array of the bundles in which the field
+   *     appears, where the keys and values are both the bundle's machine name.
    */
   public function getFieldMap();
 
@@ -97,7 +98,8 @@ interface EntityFieldManagerInterface {
    *   An array keyed by entity type. Each value is an array which keys are
    *   field names and value is an array with two entries:
    *   - type: The field type.
-   *   - bundles: The bundles in which the field appears.
+   *   - bundles: An associative array of the bundles in which the field
+   *     appears, where the keys and values are both the bundle's machine name.
    */
   public function getFieldMapByFieldType($field_type);