diff --git a/VERSION b/VERSION
index da1db37dac..e0b18b8b3b 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2021.09-dev
+2021.09-rc
diff --git a/boot.php b/boot.php
index 7ee023b68a..9c3be4a429 100644
--- a/boot.php
+++ b/boot.php
@@ -38,7 +38,7 @@ use Friendica\Util\DateTimeFormat;
 
 define('FRIENDICA_PLATFORM',     'Friendica');
 define('FRIENDICA_CODENAME',     'Siberian Iris');
-define('FRIENDICA_VERSION',      '2021.09-dev');
+define('FRIENDICA_VERSION',      '2021.09-rc');
 define('DFRN_PROTOCOL_VERSION',  '2.23');
 define('NEW_TABLE_STRUCTURE_VERSION', 1288);