diff --git a/Makefile b/Makefile
index 54930c6b6..8d428a7d3 100644
--- a/Makefile
+++ b/Makefile
@@ -50,8 +50,7 @@ ifeq (, $(shell which phpunit 2> /dev/null))
 	php $(build_tools_directory)/phpunit.phar -c tests/phpunit.xml --coverage-clover build/php-unit.coverage.xml
 	php $(build_tools_directory)/phpunit.phar -c tests/phpunit.integration.xml --coverage-clover build/php-integration.coverage.xml
 else
-	phpunit -c tests/phpunit.xml --coverage-clover build/php-unit.coverage.xml
-	phpunit -c tests/phpunit.integration.xml --coverage-clover build/php-integration.coverage.xml
+	phpunit -c tests/phpunit.integration.xml --testsuite=integration-database --coverage-clover build/php-integration.coverage.xml
 endif
 
 test-integration:
diff --git a/lib/Db/AssignmentMapper.php b/lib/Db/AssignmentMapper.php
index 7a7f368ae..5bc49e40d 100644
--- a/lib/Db/AssignmentMapper.php
+++ b/lib/Db/AssignmentMapper.php
@@ -155,9 +155,10 @@ class AssignmentMapper extends QBMapper implements IPermissionMapper {
 	public function transferOwnership($ownerId, $newOwnerId) {
 		$params = [
 			'owner' => $ownerId,
-			'newOwner' => $newOwnerId
+			'newOwner' => $newOwnerId,
+            'type' => AssignedUsers::TYPE_USER
 		];
-		$sql = "UPDATE `{$this->tableName}`  SET `participant` = :newOwner WHERE `participant` = :owner";
+		$sql = "UPDATE `{$this->tableName}`  SET `participant` = :newOwner WHERE `participant` = :owner AND `type`= :type";
 		$stmt = $this->execute($sql, $params);
 		$stmt->closeCursor();
 	}
diff --git a/tests/integration/config/behat.yml b/tests/integration/config/behat.yml
index b8673a677..507138122 100644
--- a/tests/integration/config/behat.yml
+++ b/tests/integration/config/behat.yml
@@ -5,7 +5,7 @@ default:
         - '%paths.base%/../features/'
       contexts:
         - ServerContext:
-            baseUrl:  http://localhost:8080/
+            baseUrl:  http://localhost:9090/
         - RequestContext
         - BoardContext
         - CommentContext
diff --git a/tests/integration/database/TransferOwnershipTest.php b/tests/integration/database/TransferOwnershipTest.php
index e49e409b4..aff664640 100644
--- a/tests/integration/database/TransferOwnershipTest.php
+++ b/tests/integration/database/TransferOwnershipTest.php
@@ -13,6 +13,8 @@ use OCA\Deck\Db\Board;
 class TransferOwnershipTest extends \Test\TestCase {
 	private const TEST_OWNER = 'test-share-user1';
 	private const TEST_NEW_OWNER = 'target';
+	private const TEST_NEW_OWNER_PARTICIPANT = 'target-participant';
+	private const TEST_NEW_OWNER_IN_ACL = 'target-in-acl';
 	private const TEST_GROUP = 'test-share-user1';
 
 	/** @var BoardService */
@@ -38,6 +40,7 @@ class TransferOwnershipTest extends \Test\TestCase {
 		\OC::$server->getUserManager()->registerBackend($backend);
 		$backend->createUser(self::TEST_OWNER, self::TEST_OWNER);
 		$backend->createUser(self::TEST_NEW_OWNER, self::TEST_NEW_OWNER);
+		$backend->createUser(self::TEST_NEW_OWNER_PARTICIPANT, self::TEST_NEW_OWNER_PARTICIPANT);
 		// create group
 		$groupBackend = new \Test\Util\Group\Dummy();
 		$groupBackend->createGroup(self::TEST_GROUP);
@@ -68,6 +71,7 @@ class TransferOwnershipTest extends \Test\TestCase {
 		$cards[] = $this->cardService->create('Card 1', $stacks[0]->getId(), 'text', 0, self::TEST_OWNER);
 		$cards[] = $this->cardService->create('Card 2', $stacks[0]->getId(), 'text', 0, self::TEST_OWNER);
 		$this->assignmentService->assignUser($cards[0]->getId(), self::TEST_OWNER);
+		$this->assignmentService->assignUser($cards[0]->getId(), self::TEST_NEW_OWNER_PARTICIPANT);
 		$this->board = $board;
 		$this->cards = $cards;
 		$this->stacks = $stacks;
@@ -137,7 +141,22 @@ class TransferOwnershipTest extends \Test\TestCase {
      */
     public function testReassignCardToNewParticipantOnlyIfParticipantHasUserType() {
         $this->boardService->transferOwnership(self::TEST_OWNER, self::TEST_NEW_OWNER);
-        $this->assignmentService->ass($cards[0]->getId(), self::TEST_OWNER);
+        $this->assignmentService->ass($this->cards[0]->getId(), self::TEST_OWNER);
+        $assignedUsers = $this->assignedUsersMapper->find($this->cards[0]->getId());
+        $participantsUIDs = [];
+        foreach ($assignedUsers as $user) {
+            $participantsUIDs[] = $user->getParticipant();
+        }
+        $this->assertContains(self::TEST_NEW_OWNER, $participantsUIDs);
+        $this->assertNotContains(self::TEST_OWNER, $participantsUIDs);
+    }
+
+    /**
+     * @covers ::transferOwnership
+     */
+    public function testTargetAlreadyParticipantOfTransferedCard() {
+        $this->boardService->transferOwnership(self::TEST_OWNER, self::TEST_NEW_OWNER_PARTICIPANT);
+        $this->assignmentService->assignUser($this->cards[0]->getId(), self::TEST_OWNER);
         $assignedUsers = $this->assignedUsersMapper->find($this->cards[0]->getId());
         $participantsUIDs = [];
         foreach ($assignedUsers as $user) {
diff --git a/tests/integration/run.sh b/tests/integration/run.sh
index ab9790b26..de8b32563 100755
--- a/tests/integration/run.sh
+++ b/tests/integration/run.sh
@@ -26,7 +26,7 @@ composer dump-autoload
 if [ -z "$EXECUTOR_NUMBER" ]; then
     EXECUTOR_NUMBER=0
 fi
-PORT=$((8080 + $EXECUTOR_NUMBER))
+PORT=$((9090 + $EXECUTOR_NUMBER))
 echo $PORT
 php -S localhost:$PORT -t $OC_PATH &
 PHPPID=$!
diff --git a/tests/unit/Service/BoardServiceTest.php b/tests/unit/Service/BoardServiceTest.php
index e59662489..c64422ff5 100644
--- a/tests/unit/Service/BoardServiceTest.php
+++ b/tests/unit/Service/BoardServiceTest.php
@@ -31,6 +31,7 @@ use OCA\Deck\Db\Assignment;
 use OCA\Deck\Db\AssignmentMapper;
 use OCA\Deck\Db\Board;
 use OCA\Deck\Db\BoardMapper;
+use OCA\Deck\Db\CardMapper;
 use OCA\Deck\Db\ChangeHelper;
 use OCA\Deck\Db\LabelMapper;
 use OCA\Deck\Db\StackMapper;
@@ -58,6 +59,8 @@ class BoardServiceTest extends TestCase {
 	private $boardMapper;
 	/** @var StackMapper */
 	private $stackMapper;
+    /** @var CardMapper */
+    private $cardMapper;
 	/** @var PermissionService */
 	private $permissionService;
 	/** @var NotificationHelper */
@@ -85,6 +88,7 @@ class BoardServiceTest extends TestCase {
 		$this->boardMapper = $this->createMock(BoardMapper::class);
 		$this->stackMapper = $this->createMock(StackMapper::class);
 		$this->config = $this->createMock(IConfig::class);
+		$this->cardMapper = $this->createMock(CardMapper::class);
 		$this->labelMapper = $this->createMock(LabelMapper::class);
 		$this->permissionService = $this->createMock(PermissionService::class);
 		$this->notificationHelper = $this->createMock(NotificationHelper::class);
@@ -106,6 +110,7 @@ class BoardServiceTest extends TestCase {
 			$this->permissionService,
 			$this->notificationHelper,
 			$this->assignedUsersMapper,
+			$this->cardMapper,
 			$this->userManager,
 			$this->groupManager,
 			$this->activityManager,