diff --git a/library/Icingadb/ProvidedHook/Reporting/Common/SlaTimeline.php b/library/Icingadb/ProvidedHook/Reporting/Common/SlaTimeline.php
index 7f0a2e3de..6466f47e5 100644
--- a/library/Icingadb/ProvidedHook/Reporting/Common/SlaTimeline.php
+++ b/library/Icingadb/ProvidedHook/Reporting/Common/SlaTimeline.php
@@ -62,9 +62,9 @@ public function setInitialHardState(int $state): self
     /**
      * Get the calculated SLA result of this timeline
      *
-     * @return float
+     * @return ?float
      */
-    public function getResult(): float
+    public function getResult(): ?float
     {
         $problemTime = 0;
         $activeDowntimes = 0;
@@ -97,6 +97,10 @@ public function getResult(): float
         $this->problemTime = $problemTime;
         $this->totalTime = $totalTime;
 
+        if ($totalTime <= 0) {
+            return null;
+        }
+
         return 100 * ($totalTime - $problemTime) / $totalTime;
     }