diff --git a/apps/dav/command/migratecalendars.php b/apps/dav/command/migratecalendars.php
index 5e7f6e9b69..d887309ac3 100644
--- a/apps/dav/command/migratecalendars.php
+++ b/apps/dav/command/migratecalendars.php
@@ -61,8 +61,8 @@ class MigrateCalendars extends Command {
 	protected function execute(InputInterface $input, OutputInterface $output) {
 		$this->service->setup();
 
-		if ($input->hasArgument('user')) {
-			$user = $input->getArgument('user');
+		$user = $input->getArgument('user');
+		if (!is_null($user)) {
 			if (!$this->userManager->userExists($user)) {
 				throw new \InvalidArgumentException("User <$user> in unknown.");
 			}
diff --git a/apps/dav/command/syncbirthdaycalendar.php b/apps/dav/command/syncbirthdaycalendar.php
index 66ab540b9a..90a73a3eeb 100644
--- a/apps/dav/command/syncbirthdaycalendar.php
+++ b/apps/dav/command/syncbirthdaycalendar.php
@@ -61,8 +61,8 @@ class SyncBirthdayCalendar extends Command {
 	 * @param OutputInterface $output
 	 */
 	protected function execute(InputInterface $input, OutputInterface $output) {
-		if ($input->hasArgument('user')) {
-			$user = $input->getArgument('user');
+		$user = $input->getArgument('user');
+		if (!is_null($user)) {
 			if (!$this->userManager->userExists($user)) {
 				throw new \InvalidArgumentException("User <$user> in unknown.");
 			}