diff --git a/src/lti/LTI_Lineitem.php b/src/lti/LTI_Lineitem.php
index ba8e20a7..8608970a 100644
--- a/src/lti/LTI_Lineitem.php
+++ b/src/lti/LTI_Lineitem.php
@@ -19,8 +19,8 @@ public function __construct(array $lineitem = null) {
         $this->label = $lineitem["label"];
         $this->resource_id = $lineitem["resourceId"];
         $this->tag = $lineitem["tag"];
-        $this->start_date_time = $lineitem["startDateTime"];
-        $this->end_date_time = $lineitem["endDateTime"];
+        $this->start_date_time = $lineitem["startDateTime"] ?? null;
+        $this->end_date_time = $lineitem["endDateTime"] ?? null;
     }
 
     /**