diff --git a/src/Twig/AppTwigExtension.php b/src/Twig/AppTwigExtension.php
index c475525b552d2f5f817b66bc3ab445747331a7d6..0a005ca1d2f9c5c283b8a042aece53364a5b21d0 100644
--- a/src/Twig/AppTwigExtension.php
+++ b/src/Twig/AppTwigExtension.php
@@ -102,7 +102,7 @@ class AppTwigExtension extends AbstractExtension
         $nextMilestoneIndex = $currentMilestone < $numSuccesses - 1 ? $currentMilestone + 1 : $numSuccesses - 1;
 
 
-        $progressPercentage = ($counter - $successMilestones[$currentMilestone]) / ($successMilestones[$currentMilestone+1] - $currentMilestone) * 100; // Calculate progress percentage
+        $progressPercentage = ($counter - $successMilestones[$currentMilestone]) / ($successMilestones[min($currentMilestone+1, $numSuccesses-1)] - $currentMilestone) * 100; // Calculate progress percentage
         // Define CSS styles for the progress bar container and fill
         $containerStyle = sprintf('background-color: %s;', $successColors[1]); // Use the first color in $successColors for the container background
         $fillStyle = sprintf('background-color: %s; width: %s%%;', $successColors[0], $progressPercentage); // Use the second color in $successColors for the fill