diff --git a/src/Models/Monitor.php b/src/Models/Monitor.php
index 127358c0..0be06bf4 100644
--- a/src/Models/Monitor.php
+++ b/src/Models/Monitor.php
@@ -112,7 +112,11 @@ public function getRemainingSecondsAttribute(): ?float
             return null;
         }
 
-        $secondsRunning = now()->getTimestamp() - $this->created_at->getTimestamp();
+        if (!$this->started_at) {
+            return null;
+        }
+
+        $secondsRunning = now()->getTimestamp() - $this->started_at->getTimestamp();
 
         return (float) ($secondsRunning - ($secondsRunning * $this->progress / 100));
     }