diff --git a/library/Perfdatagraphsprometheus/Client/Prometheus.php b/library/Perfdatagraphsprometheus/Client/Prometheus.php
index 034b85f..57bc2d4 100644
--- a/library/Perfdatagraphsprometheus/Client/Prometheus.php
+++ b/library/Perfdatagraphsprometheus/Client/Prometheus.php
@@ -115,14 +115,19 @@ protected function getAuth(): array
     }
 
     /**
-     * calculateSteps uses the start and end timestamps to calculate the step parameter
+     * calculateSteps uses the start and end timestamps to calculate the step parameter.
+     *
+     * The step is never smaller than $checkInterval to avoid repeated identical
+     * values caused by Prometheus gap-filling within the lookback window.
      */
-    protected function calculateSteps(int $start, int $end, int $maxDataPoints): string
+    protected function calculateSteps(int $start, int $end, int $maxDataPoints, int $checkInterval = 0): string
     {
         $totalSeconds = $end - $start;
         $stepSeconds = $totalSeconds / $maxDataPoints;
-        // NOTE: This means we can never get a resolution below 60s, even if Icinga2 would send data every 15s
-        $stepSeconds = max($stepSeconds, 60);
+        // Use the check interval as the minimum step so we don't over-sample.
+        // Fall back to 1s when no check interval is available.
+        $minStep = $checkInterval > 0 ? $checkInterval : 1;
+        $stepSeconds = max($stepSeconds, $minStep);
 
         return (int)round($stepSeconds) . 's';
     }
@@ -134,7 +139,8 @@ public function getMetrics(
         string $from,
         bool $isHostCheck,
         array $includeMetrics,
-        array $excludeMetrics
+        array $excludeMetrics,
+        int $checkInterval = 0
     ): Response {
         $endTime = new DateTimeImmutable();
         $startTime = $endTime->sub(new DateInterval($from));
@@ -145,7 +151,7 @@ public function getMetrics(
 
         $start = $startTime->getTimestamp();
         $end = $endTime->getTimestamp();
-        $step = $this->calculateSteps($start, $end, $this->maxDataPoints);
+        $step = $this->calculateSteps($start, $end, $this->maxDataPoints, $checkInterval);
 
         $query = [
             'query' => [
diff --git a/library/Perfdatagraphsprometheus/Client/Transformer.php b/library/Perfdatagraphsprometheus/Client/Transformer.php
index 45933b0..e003e8f 100644
--- a/library/Perfdatagraphsprometheus/Client/Transformer.php
+++ b/library/Perfdatagraphsprometheus/Client/Transformer.php
@@ -46,8 +46,8 @@ protected static function preparePerfdataResponse(array $results, PerfdataRespon
             $timestamps = [];
 
             foreach ($result['values'] as $point) {
-                $timestamps[] = $point[0];
-                $values[] = $point[1];
+                $timestamps[] = (int) $point[0];
+                $values[] = is_numeric($point[1]) ? (float) $point[1] : null;
             }
 
             $valuesSeries = new PerfdataSeries('value', $values);
@@ -95,11 +95,15 @@ protected static function appendThresholds(array $results, PerfdataResponse $pfr
             }
 
             $ts = $dataset->getTimestamps();
-            $valueMap = array_column($result['values'], 1, 0);
-            // Get the matching threshold value for the given timestamp otherwise use null
+            // Build a map of timestamp (int) => float value for fast lookup.
+            $valueMap = [];
+            foreach ($result['values'] as $point) {
+                $valueMap[(int) $point[0]] = is_numeric($point[1]) ? (float) $point[1] : null;
+            }
+            // Align threshold values to the stored timestamps; use null for gaps.
             $thresholds = [];
             foreach ($ts as $timestamp) {
-                $thresholds[] = $valueMap[$timestamp] ?? null;
+                $thresholds[] = $valueMap[(int) $timestamp] ?? null;
             }
 
             $thresholdSeries = new PerfdataSeries($thresholdType, $thresholds);
diff --git a/library/Perfdatagraphsprometheus/ProvidedHook/Perfdatagraphs/PerfdataSource.php b/library/Perfdatagraphsprometheus/ProvidedHook/Perfdatagraphs/PerfdataSource.php
index 45a1fa3..686e247 100644
--- a/library/Perfdatagraphsprometheus/ProvidedHook/Perfdatagraphs/PerfdataSource.php
+++ b/library/Perfdatagraphsprometheus/ProvidedHook/Perfdatagraphs/PerfdataSource.php
@@ -45,7 +45,8 @@ public function fetchData(PerfdataRequest $req): PerfdataResponse
                 $req->getDuration(),
                 $req->isHostCheck(),
                 $req->getIncludeMetrics(),
-                $req->getExcludeMetrics()
+                $req->getExcludeMetrics(),
+                $req->getCheckInterval()
             );
         } catch (ConnectException $e) {
             $perfdataresponse->addError($e->getMessage());