diff --git a/plugins/Goals/Goals.php b/plugins/Goals/Goals.php
index d3e76f951d8..420a52a88ac 100644
--- a/plugins/Goals/Goals.php
+++ b/plugins/Goals/Goals.php
@@ -310,7 +310,7 @@ public function getReportMetadataEnd(&$reports, $info)
 
         $reportsWithGoals = self::getAllReportsWithGoalMetrics();
 
-        foreach ($reports as &$apiReportToUpdate) {
+        foreach ($reports as $index => &$apiReportToUpdate) {
             $reportHasGoals = false;
             foreach ($reportsWithGoals as $reportWithGoals) {
                 if (
@@ -327,6 +327,10 @@ public function getReportMetadataEnd(&$reports, $info)
                 continue;
             }
 
+            if (empty($apiReportToUpdate)) { // TODO: remove after done debugging
+                throw new \Exception("found empty report at $index");
+            }
+
             // collect extra metrics and processed metrics
             $extraProcessedMetrics = [
                 new \Piwik\Plugins\Goals\Columns\Metrics\RevenuePerVisit($allIdGoals),