diff --git a/libraries/tbl_relation.lib.php b/libraries/tbl_relation.lib.php
index 0fce27bbac..ca7b6e3882 100644
--- a/libraries/tbl_relation.lib.php
+++ b/libraries/tbl_relation.lib.php
@@ -166,14 +166,14 @@ function PMA_generateRelationalDropdown(
 /**
  * Function to get html for the common form
  *
- * @param string $db                 current database
- * @param string $table              current table
- * @param array  $columns            columns
- * @param array  $cfgRelation        configuration relation
- * @param string $tbl_storage_engine table storage engine
- * @param array  $existrel           db, table, column
- * @param array  $existrel_foreign   db, table, column
- * @param array  $options_array      options array
+ * @param string     $db                 current database
+ * @param string     $table              current table
+ * @param array      $columns            columns
+ * @param array      $cfgRelation        configuration relation
+ * @param string     $tbl_storage_engine table storage engine
+ * @param array|null $existrel           db, table, column
+ * @param array|null $existrel_foreign   db, table, column
+ * @param array      $options_array      options array
  *
  * @return string
  */