diff --git a/plugins/VisitsSummary/Reports/Get.php b/plugins/VisitsSummary/Reports/Get.php
index 4c197fc652c10e0a4a7b93366e7766e2ea649c33..ba6d2e94ba671708f664cdc8bccd95802de36b60 100644
--- a/plugins/VisitsSummary/Reports/Get.php
+++ b/plugins/VisitsSummary/Reports/Get.php
@@ -181,7 +181,7 @@ class Get extends \Piwik\Plugin\Report
         }
 
         $userId = new UserId();
-        if ($userId->isUsedInAtLeastOneSite($currentIdSite, $currentPeriod, $currentDate)) {
+        if ($userId->isUsedInAtLeastOneSite(array($currentIdSite), $currentPeriod, $currentDate)) {
             $view->config->addSparklineMetric(array('nb_users'), 30);
             $view->config->addPlaceholder(31);
         }