diff --git a/src/IndexInterface.php b/src/IndexInterface.php
index 277f76c1..2c7e1da4 100644
--- a/src/IndexInterface.php
+++ b/src/IndexInterface.php
@@ -399,19 +399,15 @@ interface IndexInterface extends ConfigEntityInterface {
   /**
    * Adds a field to this index.
    *
-   * If the field is already present (with the same datasource and property
-   * path) its settings will be updated.
-   *
    * @param \Drupal\search_api\Item\FieldInterface $field
-   *   The field to add, or update.
+   *   The field to add.
    *
    * @return $this
    *
    * @throws \Drupal\search_api\SearchApiException
-   *   Thrown if the field could not be added, either because a different field
-   *   with the same field ID would be overwritten, or because the field
-   *   identifier is one of the pseudo-fields that can be used in search
-   *   queries.
+   *   Thrown if the field could not be added, either because a field with the
+   *   same field ID already exists, or because the field identifier is one of
+   *   the pseudo-fields that can be used in search queries.
    */
   public function addField(FieldInterface $field);