diff --git a/lib/filelib.php b/lib/filelib.php
index 5b7628a63a6..c660e49942b 100644
--- a/lib/filelib.php
+++ b/lib/filelib.php
@@ -1878,7 +1878,7 @@ function file_get_typegroup($element, $groups) {
         }
         $result = array_merge($result, $cached[$element][$group]);
     }
-    return array_unique($result);
+    return array_values(array_unique($result));
 }
 
 /**