diff --git a/typo3/sysext/seo/Classes/XmlSitemap/AbstractXmlSitemapDataProvider.php b/typo3/sysext/seo/Classes/XmlSitemap/AbstractXmlSitemapDataProvider.php
index 42e9f7b3ea0350779bb78f1a1c58e2952b321fe2..738e12a3467cf313312fc50ae53bba24d37a4165 100644
--- a/typo3/sysext/seo/Classes/XmlSitemap/AbstractXmlSitemapDataProvider.php
+++ b/typo3/sysext/seo/Classes/XmlSitemap/AbstractXmlSitemapDataProvider.php
@@ -104,7 +104,7 @@ abstract class AbstractXmlSitemapDataProvider implements XmlSitemapDataProviderI
     {
         $lastMod = 0;
         foreach ($this->items as $item) {
-            if ((int)$item['lastMod'] > $lastMod) {
+            if ((int)($item['lastMod'] ?? 0) > $lastMod) {
                 $lastMod = (int)$item['lastMod'];
             }
         }