diff --git a/src/Protocol/Diaspora.php b/src/Protocol/Diaspora.php
index 9e80c13028..1bfe1ca652 100644
--- a/src/Protocol/Diaspora.php
+++ b/src/Protocol/Diaspora.php
@@ -4133,6 +4133,17 @@ class Diaspora
 			return false;
 		}
 
+		$parent_post = Post::selectFirstPost(['gravity', 'signed_text', 'author-link'], ['uri-id' => $item['thr-parent-id']]);
+		if (empty(FContact::getByURL($parent_post['author-link'], false))) {
+			Logger::info('Parent author is no Diaspora contact. A signature will not be created.', ['uri-id' => $item['uri-id'], 'guid' => $item['guid']]);
+			return false;
+		}
+
+		if (($parent_post['gravity'] == GRAVITY_COMMENT) && empty($parent_post['signed_text'])) {
+			Logger::info('Parent comment has got no Diaspora signature. A signature will not be created.', ['uri-id' => $item['uri-id'], 'guid' => $item['guid']]);
+			return false;
+		}
+
 		$message = self::constructComment($item, $owner);
 		if ($message === false) {
 			return false;
diff --git a/src/Worker/Notifier.php b/src/Worker/Notifier.php
index 3b4e1478c0..7d3d3d6b7c 100644
--- a/src/Worker/Notifier.php
+++ b/src/Worker/Notifier.php
@@ -191,6 +191,10 @@ class Notifier
 			// when the original comment author does support the Diaspora protocol.
 			if ($thr_parent['author-link'] && $target_item['parent-uri'] != $target_item['thr-parent']) {
 				$diaspora_delivery = Diaspora::isSupportedByContactUrl($thr_parent['author-link']);
+				if ($diaspora_delivery &&  empty($target_item['signed_text'])) {
+					Logger::debug('Post has got no Diaspora signature, so there will be no Diaspora delivery', ['guid' => $target_item['guid'], 'uri-id' => $target_item['uri-id']]);
+					$diaspora_delivery = false;
+				}
 				Logger::info('Threaded comment', ['diaspora_delivery' => (int)$diaspora_delivery]);
 			}