diff --git a/amp.php b/amp.php
index 85bd156d30b..b724089dc1b 100644
--- a/amp.php
+++ b/amp.php
@@ -5,7 +5,7 @@
  * Plugin URI: https://amp-wp.org
  * Author: AMP Project Contributors
  * Author URI: https://github.com/ampproject/amp-wp/graphs/contributors
- * Version: 2.5.5
+ * Version: 2.5.6-alpha
  * License: GPLv2 or later
  * License URI: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
  * Requires at least: 6.5
@@ -17,7 +17,7 @@
 
 define( 'AMP__FILE__', __FILE__ );
 define( 'AMP__DIR__', dirname( __FILE__ ) );
-define( 'AMP__VERSION', '2.5.5' );
+define( 'AMP__VERSION', '2.5.6-alpha' );
 
 /**
  * Errors encountered while loading the plugin.