diff --git a/src/helpers/get-assignee-activity.ts b/src/helpers/get-assignee-activity.ts
index 78679cc..2468cde 100644
--- a/src/helpers/get-assignee-activity.ts
+++ b/src/helpers/get-assignee-activity.ts
@@ -38,7 +38,7 @@ function filterEvents(issueEvents: GitHubTimelineEvents[], assigneeIds: number[]
   for (const event of issueEvents) {
     let actorId = null;
     let actorLogin = null;
-    let createdAt = "UNKNOWN";
+    let createdAt = null;
     let eventName = event.event;
 
     if ("actor" in event && event.actor) {
@@ -71,6 +71,9 @@ function filterEvents(issueEvents: GitHubTimelineEvents[], assigneeIds: number[]
   }
 
   return assigneeEvents.sort((a, b) => {
+    if (!a.created_at || !b.created_at) {
+      return 0;
+    }
     return DateTime.fromISO(b.created_at).toMillis() - DateTime.fromISO(a.created_at).toMillis();
   });
 }
diff --git a/src/helpers/task-deadline.ts b/src/helpers/task-deadline.ts
index 7b62079..555fb07 100644
--- a/src/helpers/task-deadline.ts
+++ b/src/helpers/task-deadline.ts
@@ -35,18 +35,24 @@ export async function getDeadlineWithThreshold(
   }
 
   const activity = (await getAssigneesActivityForIssue(context, issue, assigneeIds)).filter((o) => {
+    if (!o.created_at) {
+      return false;
+    }
     return DateTime.fromISO(o.created_at) > lastCheck;
   });
 
   const filteredActivity = activity.filter((o) => {
-    return eventWhitelist.includes(o.event || "");
+    if (!o.event) {
+      return false;
+    }
+    return eventWhitelist.includes(o.event);
   });
 
   let deadlineWithThreshold = deadline.plus({ milliseconds: disqualification });
   let reminderWithThreshold = deadline.plus({ milliseconds: warning });
 
   if (filteredActivity?.length) {
-    const lastActivity = DateTime.fromISO(filteredActivity[0].created_at);
+    const lastActivity = filteredActivity[0].created_at ? DateTime.fromISO(filteredActivity[0].created_at) : deadline;
     deadlineWithThreshold = lastActivity.plus({ milliseconds: disqualification });
     reminderWithThreshold = lastActivity.plus({ milliseconds: warning });
   }