diff --git a/src/Plugin/search_api/processor/FilesExtrator.php b/src/Plugin/search_api/processor/FilesExtrator.php
index 8b39a14..10cd218 100644
--- a/src/Plugin/search_api/processor/FilesExtrator.php
+++ b/src/Plugin/search_api/processor/FilesExtrator.php
@@ -499,7 +499,7 @@ class FilesExtrator extends ProcessorPluginBase {
     else {
 
       if (!$extensions) {
-        $extensions = $this->defaultExcludedExtensions();
+        $extensions = explode(' ', $this->defaultExcludedExtensions());
       }
       $excluded_mimes = [];
       foreach ($extensions as $extension) {