diff --git a/src/Prometheus/Storage/APC.php b/src/Prometheus/Storage/APC.php
index 1e4b24c8..c45f1940 100644
--- a/src/Prometheus/Storage/APC.php
+++ b/src/Prometheus/Storage/APC.php
@@ -383,7 +383,7 @@ private function collectHistograms(): array
                     'name' => $metaData['name'] . '_sum',
                     'labelNames' => [],
                     'labelValues' => $decodedLabelValues,
-                    'value' => $this->fromBinaryRepresentationAsInteger($histogramBuckets[$labelValues]['sum']),
+                    'value' => $this->fromBinaryRepresentationAsInteger($histogramBuckets[$labelValues]['sum'] ?? 0),
                 ];
             }
             $histograms[] = new MetricFamilySamples($data);
diff --git a/src/Prometheus/Storage/APCng.php b/src/Prometheus/Storage/APCng.php
index ed468675..6628ef97 100644
--- a/src/Prometheus/Storage/APCng.php
+++ b/src/Prometheus/Storage/APCng.php
@@ -661,7 +661,7 @@ private function collectHistograms(): array
                     'name' => $metaData['name'] . '_sum',
                     'labelNames' => [],
                     'labelValues' => $decodedLabelValues,
-                    'value' => $this->convertIncrementalIntegerToFloat($histogramBuckets[$labelValues]['sum']),
+                    'value' => $this->convertIncrementalIntegerToFloat($histogramBuckets[$labelValues]['sum'] ?? 0),
                 ];
             }
             $histograms[] = new MetricFamilySamples($data);