diff --git a/src/WebThumbnailer/Finder/DefaultFinder.php b/src/WebThumbnailer/Finder/DefaultFinder.php
index 8f463c0..4a553af 100644
--- a/src/WebThumbnailer/Finder/DefaultFinder.php
+++ b/src/WebThumbnailer/Finder/DefaultFinder.php
@@ -56,7 +56,7 @@ public function find()
             $content
         );
 
-        if (empty($thumbnail) && ImageUtils::isImageString($content)) {
+        if (empty($thumbnail) && !empty($content) && ImageUtils::isImageString($content)) {
             return $this->url;
         }