diff --git a/lib/Chat/SystemMessage/Listener.php b/lib/Chat/SystemMessage/Listener.php
index b06aa26aaac..c9e591dae24 100644
--- a/lib/Chat/SystemMessage/Listener.php
+++ b/lib/Chat/SystemMessage/Listener.php
@@ -150,6 +150,10 @@ public static function register(IEventDispatcher $dispatcher): void {
 		$dispatcher->addListener(Room::EVENT_AFTER_TYPE_SET, static function (ModifyRoomEvent $event) {
 			$room = $event->getRoom();
 
+			if ($event->getOldValue() === Room::ONE_TO_ONE_CALL) {
+				return;
+			}
+
 			if ($event->getNewValue() === Room::PUBLIC_CALL) {
 				/** @var self $listener */
 				$listener = \OC::$server->query(self::class);
diff --git a/lib/Listener/UserDeletedListener.php b/lib/Listener/UserDeletedListener.php
index c12a3fd9b10..47ad1b723c4 100644
--- a/lib/Listener/UserDeletedListener.php
+++ b/lib/Listener/UserDeletedListener.php
@@ -52,7 +52,6 @@ public function handle(Event $event): void {
 		$user = $event->getUser();
 
 		$rooms = $this->manager->getRoomsForUser($user->getUID());
-
 		foreach ($rooms as $room) {
 			if ($this->participantService->getNumberOfUsers($room) === 1) {
 				$room->deleteRoom();
@@ -60,5 +59,13 @@ public function handle(Event $event): void {
 				$this->participantService->removeUser($room, $user, Room::PARTICIPANT_REMOVED);
 			}
 		}
+
+		$leftRooms = $this->manager->getLeftOneToOneRoomsForUser($user->getUID());
+		foreach ($leftRooms as $room) {
+			// We are changing the room type and name so a potential follow up
+			// user with the same user-id can not reopen the one-to-one conversation.
+			$room->setType(Room::GROUP_CALL, true);
+			$room->setName($user->getDisplayName(), '');
+		}
 	}
 }
diff --git a/lib/Manager.php b/lib/Manager.php
index a7c529c3f34..8edaeda4cb1 100644
--- a/lib/Manager.php
+++ b/lib/Manager.php
@@ -342,6 +342,34 @@ public function getRoomsForUser(string $userId, bool $includeLastMessage = false
 		return $rooms;
 	}
 
+	/**
+	 * @param string $userId
+	 * @return Room[]
+	 */
+	public function getLeftOneToOneRoomsForUser(string $userId): array {
+		$query = $this->db->getQueryBuilder();
+		$helper = new SelectHelper();
+		$helper->selectRoomsTable($query);
+		$query->from('talk_rooms', 'r')
+			->where($query->expr()->eq('r.type', $query->createNamedParameter(Room::ONE_TO_ONE_CALL)))
+			->andWhere($query->expr()->like('r.name', $query->createNamedParameter('%' . $this->db->escapeLikeParameter(json_encode($userId)) . '%')));
+
+		$result = $query->execute();
+		$rooms = [];
+		while ($row = $result->fetch()) {
+			if ($row['token'] === null) {
+				// FIXME Temporary solution for the Talk6 release
+				continue;
+			}
+
+			$room = $this->createRoomObject($row);
+			$rooms[] = $room;
+		}
+		$result->closeCursor();
+
+		return $rooms;
+	}
+
 	/**
 	 * @param string $userId
 	 * @return string[]
diff --git a/lib/Room.php b/lib/Room.php
index 4721ff41aee..8084a9f1ace 100644
--- a/lib/Room.php
+++ b/lib/Room.php
@@ -754,12 +754,12 @@ public function setAssignedSignalingServer(?int $signalingServer): bool {
 	 * @param int $newType Currently it is only allowed to change between `self::GROUP_CALL` and `self::PUBLIC_CALL`
 	 * @return bool True when the change was valid, false otherwise
 	 */
-	public function setType(int $newType): bool {
+	public function setType(int $newType, bool $allowSwitchingOneToOne = false): bool {
 		if ($newType === $this->getType()) {
 			return true;
 		}
 
-		if ($this->getType() === self::ONE_TO_ONE_CALL) {
+		if (!$allowSwitchingOneToOne && $this->getType() === self::ONE_TO_ONE_CALL) {
 			return false;
 		}
 
diff --git a/tests/integration/features/conversation/delete-user.feature b/tests/integration/features/conversation/delete-user.feature
index b20dc8a2bc4..c211a25a59d 100644
--- a/tests/integration/features/conversation/delete-user.feature
+++ b/tests/integration/features/conversation/delete-user.feature
@@ -16,6 +16,23 @@ Feature: conversation/delete-user
     Then user "participant1" sees the following messages in room "one-to-one room" with 200
       | room            | actorType     | actorId       | actorDisplayName | message   | messageParameters |
       | one-to-one room | deleted_users | deleted_users |                  | Message 1 | []                |
+    Then user "participant1" is participant of the following rooms (v4)
+      | name                     | type     |
+      | participant2-displayname | 2        |
+
+  Scenario: delete user who left a one-to-one room
+    Given user "participant1" creates room "one-to-one room" (v4)
+      | roomType | 1 |
+      | invite   | participant2 |
+    And user "participant2" sends message "Message 1" to room "one-to-one room" with 201
+    When user "participant2" leaves room "one-to-one room" with 200 (v4)
+    When user "participant2" is deleted
+    Then user "participant1" sees the following messages in room "one-to-one room" with 200
+      | room            | actorType     | actorId       | actorDisplayName | message   | messageParameters |
+      | one-to-one room | deleted_users | deleted_users |                  | Message 1 | []                |
+    Then user "participant1" is participant of the following rooms (v4)
+      | name                     | type     |
+      | participant2-displayname | 2        |
 
   Scenario: delete user who is in a group room
     Given user "participant1" creates room "group room"