diff --git a/typo3/sysext/indexed_search/Classes/Indexer.php b/typo3/sysext/indexed_search/Classes/Indexer.php
index d13b7ff1312e7b801ab977eabd7539233e051b44..32c1b80cfcb09d870e17203b097ee1e71af14c08 100644
--- a/typo3/sysext/indexed_search/Classes/Indexer.php
+++ b/typo3/sysext/indexed_search/Classes/Indexer.php
@@ -451,8 +451,8 @@ class Indexer
         $this->setT3Hashes();
         // Indexer configuration from Extension Manager interface:
         $this->indexerConfig = GeneralUtility::makeInstance(ExtensionConfiguration::class)->get('indexed_search');
-        $this->tstamp_minAge = MathUtility::forceIntegerInRange($this->indexerConfig['minAge'] * 3600, 0);
-        $this->tstamp_maxAge = MathUtility::forceIntegerInRange($this->indexerConfig['maxAge'] * 3600, 0);
+        $this->tstamp_minAge = MathUtility::forceIntegerInRange((int)($this->indexerConfig['minAge'] ?? 0) * 3600, 0);
+        $this->tstamp_maxAge = MathUtility::forceIntegerInRange((int)($this->indexerConfig['maxAge'] ?? 0) * 3600, 0);
         $this->maxExternalFiles = MathUtility::forceIntegerInRange($this->indexerConfig['maxExternalFiles'], 0, 1000, 5);
         $this->flagBitMask = MathUtility::forceIntegerInRange($this->indexerConfig['flagBitMask'], 0, 255);
         // Workaround: If the extension configuration was not updated yet, the value is not existing