diff --git a/docs/guide/db-migrations.md b/docs/guide/db-migrations.md
index adc9751..a971bb2 100644
--- a/docs/guide/db-migrations.md
+++ b/docs/guide/db-migrations.md
@@ -293,7 +293,7 @@ line:
   migration history information. It defaults to `migration`. The table
   structure is `version varchar(255) primary key, apply_time integer`.
 
-* `connectionID`: string, specifies the ID of the database application component.
+* `db`: string, specifies the ID of the database application component.
   Defaults to 'db'.
 
 * `templateFile`: string, specifies the path of the file to be served as the code
diff --git a/framework/db/Migration.php b/framework/db/Migration.php
index 6326636..6369df1 100644
--- a/framework/db/Migration.php
+++ b/framework/db/Migration.php
@@ -40,7 +40,10 @@ class Migration extends Component implements MigrationInterface
 {
     /**
      * @var Connection|string the DB connection object or the application component ID of the DB connection
-     * that this migration should work with.
+     * that this migration should work with. Note that when a Migration object is created by
+     * the `migrate` command, this property will be overwritten by the command. If you do not want to
+     * use the DB connection provided by the command, you may override the [[init()]] method
+     * and set this property after calling `parent::init()`.
      */
     public $db = 'db';