diff --git a/src/Model/Contact.php b/src/Model/Contact.php
index ae715840eb..3b65f2af1f 100644
--- a/src/Model/Contact.php
+++ b/src/Model/Contact.php
@@ -1959,7 +1959,7 @@ class Contact
 		}
 
 		// If Probe::uri fails the network code will be different ("feed" or "unkn")
-		if (in_array($ret['network'], [Protocol::FEED, Protocol::PHANTOM]) && ($ret['network'] != $contact['network'])) {
+		if (($ret['network'] == Protocol::PHANTOM) || (($ret['network'] == Protocol::FEED) && ($ret['network'] != $contact['network']))) {
 			self::updateContact($id, $uid, $contact['url'], $ret['url'], ['failed' => true, 'last-update' => $updated, 'failure_update' => $updated]);
 			return false;
 		}
diff --git a/src/Model/Item.php b/src/Model/Item.php
index 48652a0e12..299736d14d 100644
--- a/src/Model/Item.php
+++ b/src/Model/Item.php
@@ -970,6 +970,10 @@ class Item
 			unset($item['event-id']);
 		}
 
+		if (empty($item['causer-id'])) {
+			unset($item['causer-id']);
+		}
+
 		Post::insert($item['uri-id'], $item);
 
 		if ($item['gravity'] == GRAVITY_PARENT) {
diff --git a/src/Model/Post.php b/src/Model/Post.php
index 002ddbc07a..51f74ced5c 100644
--- a/src/Model/Post.php
+++ b/src/Model/Post.php
@@ -285,7 +285,7 @@ class Post
 		$condition = DBA::mergeConditions($condition,
 			["`visible` AND NOT `deleted`
 			AND NOT `author-blocked` AND NOT `owner-blocked`
-			AND (NOT `causer-blocked` OR `causer-id` = ?) AND NOT `contact-blocked`
+			AND (NOT `causer-blocked` OR `causer-id` = ? OR `causer-id` IS NULL) AND NOT `contact-blocked`
 			AND ((NOT `contact-readonly` AND NOT `contact-pending` AND (`contact-rel` IN (?, ?)))
 				OR `self` OR `gravity` != ? OR `contact-uid` = ?)
 			AND NOT EXISTS (SELECT `uri-id` FROM `post-user` WHERE `hidden` AND `uri-id` = `" . $view . "`.`uri-id` AND `uid` = ?)
diff --git a/src/Worker/UpdateContacts.php b/src/Worker/UpdateContacts.php
index 699e0f5abb..86959c88bb 100644
--- a/src/Worker/UpdateContacts.php
+++ b/src/Worker/UpdateContacts.php
@@ -49,16 +49,27 @@ class UpdateContacts
 			return;
 		}
 
-		// Add every contact our system interacted with and hadn't been updated for a week if unarchived
-		// or for a month if archived.
-		$condition = DBA::mergeConditions($base_condition, ["(`id` IN (SELECT `author-id` FROM `post-user`) OR
-			`id` IN (SELECT `owner-id` FROM `post-user`) OR `id` IN (SELECT `causer-id` FROM `post-user`) OR
-			`id` IN (SELECT `cid` FROM `post-tag`) OR `id` IN (SELECT `cid` FROM `user-contact`) OR `uid` != ?) AND
-			(`last-update` < ? OR (NOT `archive` AND `last-update` < ?))",
+		$condition = DBA::mergeConditions($base_condition,
+			["`uid` != ? AND (`last-update` < ? OR (NOT `archive` AND `last-update` < ?))",
 			0, DateTimeFormat::utc('now - 1 month'), DateTimeFormat::utc('now - 1 week')]);
-		Logger::info('Updatable interacting federated contacts', ['count' => DBA::count('contact', $condition)]);
 		$ids = self::getContactsToUpdate($condition, [], $limit);
-		Logger::info('Fetched interacting federated contacts', ['count' => count($ids)]);
+		Logger::info('Fetched federated user contacts', ['count' => count($ids)]);
+
+		$conditions = ["`id` IN (SELECT `author-id` FROM `post-user`)", "`id` IN (SELECT `owner-id` FROM `post-user`)", 
+			"`id` IN (SELECT `causer-id` FROM `post-user`)", "`id` IN (SELECT `cid` FROM `post-tag`)",
+			"`id` IN (SELECT `cid` FROM `user-contact`)"];
+
+		foreach ($conditions as $contact_condition) {
+			$condition = DBA::mergeConditions($base_condition,
+				[$contact_condition . " AND (`last-update` < ? OR (NOT `archive` AND `last-update` < ?))",
+				DateTimeFormat::utc('now - 1 month'), DateTimeFormat::utc('now - 1 week')]);
+			$ids = self::getContactsToUpdate($condition, $ids, $limit);
+			Logger::info('Fetched interacting federated contacts', ['count' => count($ids), 'condition' => $contact_condition]);
+		}
+
+		if (count($ids) > $limit) {
+			$ids = array_slice($ids, 0, $limit, true);
+		}
 
 		if (!DI::config()->get('system', 'update_active_contacts')) {
 			// Add every contact (mostly failed ones) that hadn't been updated for six months
@@ -66,7 +77,6 @@ class UpdateContacts
 			$condition = DBA::mergeConditions($base_condition,
 				["(`last-update` < ? OR (NOT `archive` AND `last-update` < ?))",
 					DateTimeFormat::utc('now - 6 month'), DateTimeFormat::utc('now - 1 month')]);
-			Logger::info('Updatable federated contacts', ['count' => DBA::count('contact', $condition)]);
 			$previous = count($ids);
 			$ids = self::getContactsToUpdate($condition, $ids, $limit - $previous);
 			Logger::info('Fetched federated contacts', ['count' => count($ids) - $previous]);
@@ -93,7 +103,7 @@ class UpdateContacts
 	{
 		$contacts = DBA::select('contact', ['id'], $condition, ['limit' => $limit, 'order' => ['last-update']]);
 		while ($contact = DBA::fetch($contacts)) {
-			$ids[] = $contact['id'];
+			$ids[$contact['id']] = $contact['id'];
 		}
 		DBA::close($contacts);
 		return $ids;
diff --git a/static/dbstructure.config.php b/static/dbstructure.config.php
index cb84e0ba91..85be690e27 100644
--- a/static/dbstructure.config.php
+++ b/static/dbstructure.config.php
@@ -55,7 +55,7 @@
 use Friendica\Database\DBA;
 
 if (!defined('DB_UPDATE_VERSION')) {
-	define('DB_UPDATE_VERSION', 1406);
+	define('DB_UPDATE_VERSION', 1407);
 }
 
 return [
@@ -993,7 +993,7 @@ return [
 			"network" => ["type" => "char(4)", "not null" => "1", "default" => "", "comment" => "Network from where the item comes from"],
 			"owner-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the owner of this item"],
 			"author-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the author of this item"],
-			"causer-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
+			"causer-id" => ["type" => "int unsigned", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
 			"post-type" => ["type" => "tinyint unsigned", "not null" => "1", "default" => "0", "comment" => "Post type (personal note, bookmark, ...)"],
 			"vid" => ["type" => "smallint unsigned", "foreign" => ["verb" => "id", "on delete" => "restrict"], "comment" => "Id of the verb table entry that contains the activity verbs"],
 			"private" => ["type" => "tinyint unsigned", "not null" => "1", "default" => "0", "comment" => "0=public, 1=private, 2=unlisted"],
@@ -1114,7 +1114,7 @@ return [
 			"uri-id" => ["type" => "int unsigned", "not null" => "1", "primary" => "1", "foreign" => ["item-uri" => "id"], "comment" => "Id of the item-uri table entry that contains the item uri"],
 			"owner-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Item owner"],
 			"author-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Item author"],
-			"causer-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
+			"causer-id" => ["type" => "int unsigned", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
 			"network" => ["type" => "char(4)", "not null" => "1", "default" => "", "comment" => ""],
 			"created" => ["type" => "datetime", "not null" => "1", "default" => DBA::NULL_DATETIME, "comment" => ""],
 			"received" => ["type" => "datetime", "not null" => "1", "default" => DBA::NULL_DATETIME, "comment" => ""],
@@ -1146,7 +1146,7 @@ return [
 			"network" => ["type" => "char(4)", "not null" => "1", "default" => "", "comment" => "Network from where the item comes from"],
 			"owner-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the owner of this item"],
 			"author-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the author of this item"],
-			"causer-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
+			"causer-id" => ["type" => "int unsigned", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
 			"post-type" => ["type" => "tinyint unsigned", "not null" => "1", "default" => "0", "comment" => "Post type (personal note, bookmark, ...)"],
 			"vid" => ["type" => "smallint unsigned", "foreign" => ["verb" => "id", "on delete" => "restrict"], "comment" => "Id of the verb table entry that contains the activity verbs"],
 			"private" => ["type" => "tinyint unsigned", "not null" => "1", "default" => "0", "comment" => "0=public, 1=private, 2=unlisted"],
@@ -1194,7 +1194,7 @@ return [
 			"uri-id" => ["type" => "int unsigned", "not null" => "1", "primary" => "1", "foreign" => ["item-uri" => "id"], "comment" => "Id of the item-uri table entry that contains the item uri"],
 			"owner-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Item owner"],
 			"author-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Item author"],
-			"causer-id" => ["type" => "int unsigned", "not null" => "1", "default" => "0", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
+			"causer-id" => ["type" => "int unsigned", "foreign" => ["contact" => "id", "on delete" => "restrict"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
 			"network" => ["type" => "char(4)", "not null" => "1", "default" => "", "comment" => ""],
 			"created" => ["type" => "datetime", "not null" => "1", "default" => DBA::NULL_DATETIME, "comment" => ""],
 			"received" => ["type" => "datetime", "not null" => "1", "default" => DBA::NULL_DATETIME, "comment" => ""],
diff --git a/update.php b/update.php
index b8d357da22..a1343255bc 100644
--- a/update.php
+++ b/update.php
@@ -885,3 +885,19 @@ function update_1404()
 		DBA::update('workerqueue', ['parameter' => json_encode($parameters)], ['id' => $task['id']]);
 	}
 }
+
+function update_1407()
+{
+	if (!DBA::e("UPDATE `post` SET `causer-id` = NULL WHERE `causer-id` = 0")) {
+		return Update::FAILED;
+	}
+	if (!DBA::e("UPDATE `post-user` SET `causer-id` = NULL WHERE `causer-id` = 0")) {
+		return Update::FAILED;
+	}
+	if (!DBA::e("UPDATE `post-thread` SET `causer-id` = NULL WHERE `causer-id` = 0")) {
+		return Update::FAILED;
+	}
+	if (!DBA::e("UPDATE `post-thread-user` SET `causer-id` = NULL WHERE `causer-id` = 0")) {
+		return Update::FAILED;
+	}
+}