diff --git a/database.sql b/database.sql
index 499ac3b033..f598ab9ccb 100644
--- a/database.sql
+++ b/database.sql
@@ -740,9 +740,11 @@ CREATE TABLE IF NOT EXISTS `item` (
 	 INDEX `uri-id` (`uri-id`),
 	 INDEX `parent-uri-id` (`parent-uri-id`),
 	 INDEX `thr-parent-id` (`thr-parent-id`),
+	 INDEX `causer-id` (`causer-id`),
 	FOREIGN KEY (`uri-id`) REFERENCES `item-uri` (`id`) ON UPDATE RESTRICT ON DELETE CASCADE,
 	FOREIGN KEY (`parent-uri-id`) REFERENCES `item-uri` (`id`) ON UPDATE RESTRICT ON DELETE CASCADE,
 	FOREIGN KEY (`thr-parent-id`) REFERENCES `item-uri` (`id`) ON UPDATE RESTRICT ON DELETE CASCADE,
+	FOREIGN KEY (`causer-id`) REFERENCES `contact` (`id`) ON UPDATE RESTRICT ON DELETE RESTRICT,
 	FOREIGN KEY (`psid`) REFERENCES `permissionset` (`id`) ON UPDATE RESTRICT ON DELETE RESTRICT
 ) DEFAULT COLLATE utf8mb4_general_ci COMMENT='Structure for all posts';
 
diff --git a/src/Model/Item.php b/src/Model/Item.php
index 970c5f4a56..d03e9ec354 100644
--- a/src/Model/Item.php
+++ b/src/Model/Item.php
@@ -775,7 +775,7 @@ class Item
 			}
 		}
 		if (strpos($sql_commands, "`causer`.") !== false) {
-			$joins .= " LEFT JOIN `contact` AS `causer` ON `causer`.`id` = $master_table.`causer-id`";
+			$joins .= " LEFT JOIN `contact` AS `causer` ON `causer`.`id` = `item`.`causer-id`";
 		}
 
 		if (strpos($sql_commands, "`group_member`.") !== false) {
diff --git a/src/Worker/MergeContact.php b/src/Worker/MergeContact.php
index 3bb4e7e689..e04dfb6ac8 100644
--- a/src/Worker/MergeContact.php
+++ b/src/Worker/MergeContact.php
@@ -55,6 +55,7 @@ class MergeContact
 			DBA::delete('post-tag', ['cid' => $old_cid]);
 			DBA::update('item', ['author-id' => $new_cid], ['author-id' => $old_cid]);
 			DBA::update('item', ['owner-id' => $new_cid], ['owner-id' => $old_cid]);
+			DBA::update('item', ['causer-id' => $new_cid], ['causer-id' => $old_cid]);
 			DBA::update('thread', ['author-id' => $new_cid], ['author-id' => $old_cid]);
 			DBA::update('thread', ['owner-id' => $new_cid], ['owner-id' => $old_cid]);
 		} else {
diff --git a/static/dbstructure.config.php b/static/dbstructure.config.php
index 2e53649b97..7e69ec034c 100755
--- a/static/dbstructure.config.php
+++ b/static/dbstructure.config.php
@@ -722,7 +722,7 @@ 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", "relation" => ["contact" => "id"], "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", "relation" => ["contact" => "id"], "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", "relation" => ["contact" => "id"], "comment" => "Link to the contact table with uid=0 of the contact that caused the item creation"],
+			"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"],
 			"icid" => ["type" => "int unsigned", "relation" => ["item-content" => "id"], "comment" => "Id of the item-content table entry that contains the whole item content"],
 			"iaid" => ["type" => "int unsigned", "relation" => ["item-activity" => "id"], "comment" => "Id of the item-activity table entry that contains the activity data"],
 			"vid" => ["type" => "smallint unsigned", "relation" => ["verb" => "id"], "comment" => "Id of the verb table entry that contains the activity verbs"],
@@ -814,6 +814,7 @@ return [
 			"uri-id" => ["uri-id"],
 			"parent-uri-id" => ["parent-uri-id"],
 			"thr-parent-id" => ["thr-parent-id"],
+			"causer-id" => ["causer-id"],
 		]
 	],
 	"item-activity" => [