diff --git a/src/Model/User.php b/src/Model/User.php
index 2a954e6e60..c329ef91a3 100644
--- a/src/Model/User.php
+++ b/src/Model/User.php
@@ -175,6 +175,14 @@ class User
 	{
 		$system_actor_name = DI::config()->get('system', 'actor_name');
 		if (!empty($system_actor_name)) {
+			$self = Contact::selectFirst(['nick'], ['uid' => 0, 'self' => true]);
+			if (!empty($self['nick'])) {
+				if ($self['nick'] != $system_actor_name) {
+					// Reset the actor name to the already used name
+					DI::config()->set('system', 'actor_name', $self['nick']);
+					$system_actor_name = $self['nick'];
+				}
+			}
 			return $system_actor_name;
 		}
 
@@ -680,7 +688,6 @@ class User
 	{
 		$forbidden_nicknames = DI::config()->get('system', 'forbidden_nicknames', '');
 		if (!empty($forbidden_nicknames)) {
-			// check if the nickname is in the list of blocked nicknames
 			$forbidden = explode(',', $forbidden_nicknames);
 			$forbidden = array_map('trim', $forbidden);
 		} else {
@@ -697,6 +704,7 @@ class User
 			return false;
 		}
 
+		// check if the nickname is in the list of blocked nicknames
 		if (in_array(strtolower($nickname), $forbidden)) {
 			return true;
 		}
diff --git a/src/Module/Admin/Site.php b/src/Module/Admin/Site.php
index 64b9395dad..de1ba5f8b3 100644
--- a/src/Module/Admin/Site.php
+++ b/src/Module/Admin/Site.php
@@ -603,7 +603,7 @@ class Site extends BaseAdmin
 			// name, label, value, help string, extra data...
 			'$sitename'         => ['sitename', DI::l10n()->t('Site name'), DI::config()->get('config', 'sitename'), ''],
 			'$sender_email'     => ['sender_email', DI::l10n()->t('Sender Email'), DI::config()->get('config', 'sender_email'), DI::l10n()->t('The email address your server shall use to send notification emails from.'), '', '', 'email'],
-			'$system_actor_name' => ['system_actor_name', DI::l10n()->t('Name of the system actor'), User::getActorName(), DI::l10n()->t("Name of the internal system account that is used to perform ActivityPub requests. This must be an unused username. If set, this shouldn't be changed again.")],
+			'$system_actor_name' => ['system_actor_name', DI::l10n()->t('Name of the system actor'), User::getActorName(), DI::l10n()->t("Name of the internal system account that is used to perform ActivityPub requests. This must be an unused username. If set, this can't be changed again.")],
 			'$banner'           => ['banner', DI::l10n()->t('Banner/Logo'), $banner, ''],
 			'$email_banner'     => ['email_banner', DI::l10n()->t('Email Banner/Logo'), $email_banner, ''],
 			'$shortcut_icon'    => ['shortcut_icon', DI::l10n()->t('Shortcut icon'), DI::config()->get('system', 'shortcut_icon'), DI::l10n()->t('Link to an icon that will be used for browsers.')],