diff --git a/mod/lockview.php b/mod/lockview.php
index 9f9dcfea42..af57730c8a 100644
--- a/mod/lockview.php
+++ b/mod/lockview.php
@@ -64,10 +64,10 @@ function lockview_content(App $a)
 	/** @var ACLFormatter $aclFormatter */
 	$aclFormatter = BaseObject::getClass(ACLFormatter::class);
 
-	$allowed_users = $aclFormatter->expand($item['allow_cid']);
-	$allowed_groups = $aclFormatter->expand($item['allow_gid']);
-	$deny_users = $aclFormatter->expand($item['deny_cid']);
-	$deny_groups = $aclFormatter->expand($item['deny_gid']);
+	$allowed_users = $aclFormatter->expand($item['allow_cid'] ?? '');
+	$allowed_groups = $aclFormatter->expand($item['allow_gid'] ?? '');
+	$deny_users = $aclFormatter->expand($item['deny_cid'] ?? '');
+	$deny_groups = $aclFormatter->expand($item['deny_gid'] ?? '');
 
 	$o = L10n::t('Visible to:') . '<br />';
 	$l = [];
diff --git a/src/Model/Item.php b/src/Model/Item.php
index 9501c8e5d2..e298cc1605 100644
--- a/src/Model/Item.php
+++ b/src/Model/Item.php
@@ -2904,10 +2904,10 @@ class Item extends BaseObject
 		/** @var ACLFormatter $aclFormater */
 		$aclFormater = self::getClass(ACLFormatter::class);
 
-		$allow_people = $aclFormater->expand($obj['allow_cid']);
-		$allow_groups = Group::expand($obj['uid'], $aclFormater->expand($obj['allow_gid']), $check_dead);
-		$deny_people  = $aclFormater->expand($obj['deny_cid']);
-		$deny_groups  = Group::expand($obj['uid'], $aclFormater->expand($obj['deny_gid']), $check_dead);
+		$allow_people = $aclFormater->expand($obj['allow_cid'] ?? '');
+		$allow_groups = Group::expand($obj['uid'], $aclFormater->expand($obj['allow_gid'] ?? ''), $check_dead);
+		$deny_people  = $aclFormater->expand($obj['deny_cid'] ?? '');
+		$deny_groups  = Group::expand($obj['uid'], $aclFormater->expand($obj['deny_gid'] ?? ''), $check_dead);
 		$recipients   = array_unique(array_merge($allow_people, $allow_groups));
 		$deny         = array_unique(array_merge($deny_people, $deny_groups));
 		$recipients   = array_diff($recipients, $deny);
diff --git a/src/Module/Item/Compose.php b/src/Module/Item/Compose.php
index c44e4c61ab..0d3b4eaac2 100644
--- a/src/Module/Item/Compose.php
+++ b/src/Module/Item/Compose.php
@@ -74,8 +74,8 @@ class Compose extends BaseModule
 				$compose_title = L10n::t('Compose new post');
 				$type = 'post';
 				$doesFederate = true;
-				$contact_allow = implode(',', $aclFormatter->expand($user['allow_cid']));
-				$group_allow = implode(',', $aclFormatter->expand($user['allow_gid'])) ?: Group::FOLLOWERS;
+				$contact_allow = implode(',', $aclFormatter->expand($user['allow_cid'] ?? ''));
+				$group_allow = implode(',', $aclFormatter->expand($user['allow_gid'] ?? '')) ?: Group::FOLLOWERS;
 				break;
 		}
 
@@ -86,8 +86,8 @@ class Compose extends BaseModule
 		$wall          = $_REQUEST['wall']          ?? $type == 'post';
 		$contact_allow = $_REQUEST['contact_allow'] ?? $contact_allow;
 		$group_allow   = $_REQUEST['group_allow']   ?? $group_allow;
-		$contact_deny  = $_REQUEST['contact_deny']  ?? implode(',', $aclFormatter->expand($user['deny_cid']));
-		$group_deny    = $_REQUEST['group_deny']    ?? implode(',', $aclFormatter->expand($user['deny_gid']));
+		$contact_deny  = $_REQUEST['contact_deny']  ?? implode(',', $aclFormatter->expand($user['deny_cid'] ?? ''));
+		$group_deny    = $_REQUEST['group_deny']    ?? implode(',', $aclFormatter->expand($user['deny_gid'] ?? ''));
 		$visibility    = ($contact_allow . $user['allow_gid'] . $user['deny_cid'] . $user['deny_gid']) ? 'custom' : 'public';
 
 		$acl_contacts = Contact::selectToArray(['id', 'name', 'addr', 'micro'], ['uid' => local_user(), 'pending' => false, 'rel' => [Contact::FOLLOWER, Contact::FRIEND]]);
diff --git a/src/Worker/Notifier.php b/src/Worker/Notifier.php
index ebc70ffb50..2b802c9e3c 100644
--- a/src/Worker/Notifier.php
+++ b/src/Worker/Notifier.php
@@ -276,10 +276,10 @@ class Notifier
 				/** @var ACLFormatter $aclFormatter */
 				$aclFormatter = BaseObject::getClass(ACLFormatter::class);
 
-				$allow_people = $aclFormatter->expand($parent['allow_cid']);
-				$allow_groups = Group::expand($uid, $aclFormatter->expand($parent['allow_gid']),true);
-				$deny_people  = $aclFormatter->expand($parent['deny_cid']);
-				$deny_groups  = Group::expand($uid, $aclFormatter->expand($parent['deny_gid']));
+				$allow_people = $aclFormatter->expand($parent['allow_cid'] ?? '');
+				$allow_groups = Group::expand($uid, $aclFormatter->expand($parent['allow_gid'] ?? ''),true);
+				$deny_people  = $aclFormatter->expand($parent['deny_cid'] ?? '');
+				$deny_groups  = Group::expand($uid, $aclFormatter->expand($parent['deny_gid'] ?? ''));
 
 				// if our parent is a public forum (forum_mode == 1), uplink to the origional author causing
 				// a delivery fork. private groups (forum_mode == 2) do not uplink
diff --git a/tests/src/Util/ACLFormaterTest.php b/tests/src/Util/ACLFormaterTest.php
index 76a566baaa..ac5b25e6c2 100644
--- a/tests/src/Util/ACLFormaterTest.php
+++ b/tests/src/Util/ACLFormaterTest.php
@@ -2,6 +2,7 @@
 
 namespace Friendica\Test\src\Util;
 
+use Error;
 use Friendica\Model\Group;
 use Friendica\Util\ACLFormatter;
 use PHPUnit\Framework\TestCase;
@@ -162,6 +163,18 @@ class ACLFormaterTest extends TestCase
 		$this->assertEquals(array('1', '3'), $aclFormatter->expand($text));
 	}
 
+	/**
+	 * Test expected exception in case of wrong typehint
+	 *
+	 * @expectedException Error
+	 */
+	public function testExpandNull()
+	{
+		$aclFormatter = new ACLFormatter();
+
+		$aclFormatter->expand(null);
+	}
+
 	public function dataAclToString()
 	{
 		return [