diff --git a/src/console/controllers/UpgradeController.php b/src/console/controllers/UpgradeController.php
index ff274714cc..f9b9d20348 100644
--- a/src/console/controllers/UpgradeController.php
+++ b/src/console/controllers/UpgradeController.php
@@ -1181,6 +1181,7 @@ public function _migrateCustomers(): void
             ->andWhere(['not', ['o.email' => null]])
             ->groupBy(['[[o.email]]'])
             ->column();
+        $guestEmails = array_filter($guestEmails);
         $this->stdoutlast('  Done. Found ' . count($guestEmails) . ' guest emails.', Console::FG_GREEN);
 
         // We know we have to make a user for every guest email address