diff --git a/Classes/Utility/ResponsiveImagesUtility.php b/Classes/Utility/ResponsiveImagesUtility.php
index f4ad6c6..9360c69 100644
--- a/Classes/Utility/ResponsiveImagesUtility.php
+++ b/Classes/Utility/ResponsiveImagesUtility.php
@@ -459,7 +459,7 @@ public function generateSrcsetImages(
 
         // Convert srcset input to array
         if (!is_array($srcset)) {
-            $srcset = GeneralUtility::trimExplode(',', $srcset);
+            $srcset = GeneralUtility::trimExplode(',', (string)$srcset);
         }
 
         $images = [];