diff --git a/src/Model/Item.php b/src/Model/Item.php
index 47af3d5a69..badf9281bb 100644
--- a/src/Model/Item.php
+++ b/src/Model/Item.php
@@ -3744,6 +3744,36 @@ class Item
 		return 0;
 	}
 
+	/**
+	 * Return the URI for a link to the post 
+	 * 
+	 * @param string $uri URI or link to post
+	 *
+	 * @return string URI
+	 */
+	public static function getURIByLink(string $uri)
+	{
+		$ssl_uri = str_replace('http://', 'https://', $uri);
+		$uris = [$uri, $ssl_uri, Strings::normaliseLink($uri)];
+
+		$item = DBA::selectFirst('item', ['uri'], ['uri' => $uris]);
+		if (DBA::isResult($item)) {
+			return $item['uri'];
+		}
+
+		$itemcontent = DBA::selectFirst('item-content', ['uri-id'], ['plink' => $uris]);
+		if (!DBA::isResult($itemcontent)) {
+			return '';
+		}
+
+		$itemuri = DBA::selectFirst('item-uri', ['uri'], ['id' => $itemcontent['uri-id']]);
+		if (DBA::isResult($itemuri)) {
+			return $itemuri['uri'];
+		}
+
+		return '';
+	}
+
 	/**
 	 * Fetches item for given URI or plink
 	 *
diff --git a/src/Protocol/ActivityPub/Processor.php b/src/Protocol/ActivityPub/Processor.php
index 9267943d5e..3bc7ff4a73 100644
--- a/src/Protocol/ActivityPub/Processor.php
+++ b/src/Protocol/ActivityPub/Processor.php
@@ -181,7 +181,7 @@ class Processor
 		}
 
 		if (empty($activity['directmessage']) && ($activity['id'] != $activity['reply-to-id']) && !Item::exists(['uri' => $activity['reply-to-id']])) {
-			Logger::log('Parent ' . $activity['reply-to-id'] . ' not found. Try to refetch it.');
+			Logger::notice('Parent not found. Try to refetch it.', ['parent' => $activity['reply-to-id']]);
 			self::fetchMissingActivity($activity['reply-to-id'], $activity);
 		}
 
diff --git a/src/Protocol/ActivityPub/Receiver.php b/src/Protocol/ActivityPub/Receiver.php
index b15ce2bc13..0ef1791413 100644
--- a/src/Protocol/ActivityPub/Receiver.php
+++ b/src/Protocol/ActivityPub/Receiver.php
@@ -503,6 +503,10 @@ class Receiver
 		// When it is an answer, we inherite the receivers from the parent
 		$replyto = JsonLD::fetchElement($activity, 'as:inReplyTo', '@id');
 		if (!empty($replyto)) {
+			// Fix possibly wrong item URI (could be an answer to a plink uri)
+			$fixedReplyTo = Item::getURIByLink($replyto);
+			$replyto = $fixedReplyTo ?: $replyto;
+
 			$parents = Item::select(['uid'], ['uri' => $replyto]);
 			while ($parent = Item::fetch($parents)) {
 				$receivers['uid:' . $parent['uid']] = $parent['uid'];
@@ -723,6 +727,15 @@ class Receiver
 		$object_data['service'] = JsonLD::fetchElement($activity, 'as:instrument', 'as:name', '@type', 'as:Service');
 		$object_data['service'] = JsonLD::fetchElement($object_data, 'service', '@value');
 
+		if (!empty($object_data['object_id'])) {
+			// Some systems (e.g. GNU Social) don't reply to the "id" field but the "uri" field.
+			$objectId = Item::getURIByLink($object_data['object_id']);
+			if (!empty($objectId) && ($object_data['object_id'] != $objectId)) {
+				Logger::notice('Fix wrong object-id', ['received' => $object_data['object_id'], 'correct' => $objectId]);
+				$object_data['object_id'] = $objectId;
+			}
+		}
+
 		return $object_data;
 	}
 
@@ -932,6 +945,13 @@ class Receiver
 		// An empty "id" field is translated to "./" by the compactor, so we have to check for this content
 		if (empty($object_data['reply-to-id']) || ($object_data['reply-to-id'] == './')) {
 			$object_data['reply-to-id'] = $object_data['id'];
+		} else {
+			// Some systems (e.g. GNU Social) don't reply to the "id" field but the "uri" field.
+			$replyToId = Item::getURIByLink($object_data['reply-to-id']);
+			if (!empty($replyToId) && ($object_data['reply-to-id'] != $replyToId)) {
+				Logger::notice('Fix wrong reply-to', ['received' => $object_data['reply-to-id'], 'correct' => $replyToId]);
+				$object_data['reply-to-id'] = $replyToId;
+			}
 		}
 
 		$object_data['published'] = JsonLD::fetchElement($object, 'as:published', '@value');