diff --git a/src/Protocol/ActivityPub/Processor.php b/src/Protocol/ActivityPub/Processor.php
index 672589a64f..6c4071f975 100644
--- a/src/Protocol/ActivityPub/Processor.php
+++ b/src/Protocol/ActivityPub/Processor.php
@@ -540,7 +540,7 @@ class Processor
 			}
 			DBA::close($replies);
 
-			if (!empty($activity['completion-mode']) && !empty($item['replies'])) {
+			if (!empty($item['replies'])) {
 				self::fetchReplies($item['replies'], $activity);
 			}
 		}
@@ -558,6 +558,8 @@ class Processor
 	 */
 	private static function fetchParent(array $activity, bool $in_background = false): string
 	{
+		$activity['callstack'] = self::addToCallstack($activity['callstack'] ?? []);
+
 		if (self::isFetched($activity['reply-to-id'])) {
 			Logger::info('Id is already fetched', ['id' => $activity['reply-to-id']]);
 			return '';
@@ -757,6 +759,8 @@ class Processor
 	 */
 	private static function getUriIdForFeaturedCollection(array $activity)
 	{
+		$activity['callstack'] = self::addToCallstack($activity['callstack'] ?? []);
+
 		$actor = APContact::getByURL($activity['actor']);
 		if (empty($actor)) {
 			return null;
@@ -1722,6 +1726,7 @@ class Processor
 				Logger::debug('Fetch announced activity', ['type' => $type, 'id' => $object_id, 'actor' => $relay_actor, 'signer' => $signer]);
 
 				if (!self::alreadyKnown($object_id, $child['id'] ?? '')) {
+					$child['callstack'] = self::addToCallstack($child['callstack'] ?? []);
 					return self::fetchMissingActivity($object_id, $child, $relay_actor, $completion, $uid);
 				}
 			}
@@ -1736,7 +1741,8 @@ class Processor
 
 		$ldactivity['recursion-depth'] = !empty($child['recursion-depth']) ? $child['recursion-depth'] + 1 : 0;
 		$ldactivity['children']        = $child['children'] ?? [];
-		// This check ist mostly superflous, since there are similar checks before. This covers the case, when the fetched id doesn't match the url
+		$ldactivity['callstack']       = $child['callstack'] ?? [];
+		// This check is mostly superfluous, since there are similar checks before. This covers the case, when the fetched id doesn't match the url
 		if (in_array($activity['id'], $ldactivity['children'])) {			
 			Logger::notice('Fetched id is already in the list of children. It will not be processed.', ['id' => $activity['id'], 'children' => $ldactivity['children'], 'depth' => count($ldactivity['children'])]);
 			return null;
@@ -1788,6 +1794,12 @@ class Processor
 
 	private static function fetchReplies(string $url, array $child)
 	{
+		if (in_array(__FUNCTION__, $child['callstack'] ?? [])) {
+			Logger::notice('Callstack already contains "' . __FUNCTION__ . '"', ['callstack' => $child['callstack']]);
+			return;
+		}
+		$child['callstack'] = self::addToCallstack($child['callstack'] ?? []);
+
 		$replies = ActivityPub::fetchItems($url);
 		if (empty($replies)) {
 			Logger::notice('No replies', ['replies' => $url]);
@@ -2572,4 +2584,25 @@ class Processor
 
 		return $body;
 	}
+
+	/**
+	 * Add the current function to the callstack
+	 *
+	 * @param array $callstack
+	 * @return array
+	 */
+	public static function addToCallstack(array $callstack): array
+	{
+		$trace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
+		$functions = array_slice(array_column($trace, 'function'), 1);
+		$function = array_shift($functions);
+
+		if (in_array($function, $callstack)) {
+			Logger::notice('Callstack already contains "' . $function . '"', ['callstack' => $callstack]);
+		}
+
+		$callstack[] = $function;
+
+		return $callstack;
+	}
 }
diff --git a/src/Protocol/ActivityPub/Queue.php b/src/Protocol/ActivityPub/Queue.php
index b2e8cb301b..a9918e5ea0 100644
--- a/src/Protocol/ActivityPub/Queue.php
+++ b/src/Protocol/ActivityPub/Queue.php
@@ -333,6 +333,7 @@ class Queue
 					return false;
 				}
 				$activity['recursion-depth'] = 0;
+				$activity['callstack'] = Processor::addToCallstack($activity['callstack'] ?? []);
 				$wid = Worker::add(Worker::PRIORITY_HIGH, 'FetchMissingActivity', $entry['in-reply-to-id'], $activity, '', Receiver::COMPLETION_ASYNC);
 				Fetch::setWorkerId($entry['in-reply-to-id'], $wid);
 				Logger::debug('Fetch missing activity', ['wid' => $wid, 'id' => $entry['activity-id'], 'reply-to-id' => $entry['in-reply-to-id']]);
diff --git a/src/Protocol/ActivityPub/Receiver.php b/src/Protocol/ActivityPub/Receiver.php
index 9660827cd3..39090df413 100644
--- a/src/Protocol/ActivityPub/Receiver.php
+++ b/src/Protocol/ActivityPub/Receiver.php
@@ -250,7 +250,6 @@ class Receiver
 		} elseif (!Fetch::hasWorker($object_id)) {
 			Logger::notice('Fetching is done by worker.', ['id' => $object_id]);
 			Fetch::add($object_id);
-			$activity['recursion-depth'] = 0;
 			$wid = Worker::add(Worker::PRIORITY_HIGH, 'FetchMissingActivity', $object_id, [], $actor, self::COMPLETION_RELAY);
 			Fetch::setWorkerId($object_id, $wid);
 		} else {
@@ -757,7 +756,8 @@ class Receiver
 			$object_data['recursion-depth'] = $activity['recursion-depth'];
 		}
 
-		$object_data['children'] = $activity['children'] ?? [];
+		$object_data['children']  = $activity['children'] ?? [];
+		$object_data['callstack'] = $activity['callstack'] ?? [];
 
 		if (!self::routeActivities($object_data, $type, $push, true, $uid)) {
 			self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);