diff --git a/src/Bundle/ChillActivityBundle/Export/Aggregator/SentReceivedAggregator.php b/src/Bundle/ChillActivityBundle/Export/Aggregator/SentReceivedAggregator.php
index 2a6dec7f7..24000096f 100644
--- a/src/Bundle/ChillActivityBundle/Export/Aggregator/SentReceivedAggregator.php
+++ b/src/Bundle/ChillActivityBundle/Export/Aggregator/SentReceivedAggregator.php
@@ -48,6 +48,9 @@ class SentReceivedAggregator implements AggregatorInterface
             }
 
             switch ($value) {
+                case null:
+                    return '';
+
                 case 'sent':
                     return 'is sent';