diff --git a/search_api_db/src/Plugin/search_api/backend/Database.php b/search_api_db/src/Plugin/search_api/backend/Database.php
index 49ed064..c9a3653 100644
--- a/search_api_db/src/Plugin/search_api/backend/Database.php
+++ b/search_api_db/src/Plugin/search_api/backend/Database.php
@@ -580,10 +580,10 @@ class Database extends BackendPluginBase {
     }
     $this->database->schema()->addField($db['table'], $db['column'], $db_field);
     if ($db_field['type'] === 'varchar') {
-      $this->database->schema()->addIndex($db['table'], $db['column'], array(array($db['column'], 10)));
+      $this->database->schema()->addIndex($db['table'], $db['column'], array(array($db['column'], [10])), $this->database->schema()->getFieldTypeMap());
     }
     else {
-      $this->database->schema()->addIndex($db['table'], $db['column'], array($db['column']));
+      $this->database->schema()->addIndex($db['table'], $db['column'], array($db['column']), $this->database->schema()->getFieldTypeMap());
     }
     if ($new_table) {
       // Add a covering index for fields with multiple values.