diff --git a/src/DropzoneFile.php b/src/DropzoneFile.php
index 96220a1..8eb98fd 100644
--- a/src/DropzoneFile.php
+++ b/src/DropzoneFile.php
@@ -83,7 +83,7 @@ public function getPreviewThumbnail($w = null, $h = null)
      */
     protected function getFilenameForType($ext, $size)
     {
-        return ModuleResourceLoader::singleton()->resolveResource(sprintf(
+        return ModuleResourceLoader::singleton()->resolveURL(sprintf(
             'unclecheese/dropzone:images/file-icons/%spx/%s.png',
             $size,
             strtolower($ext)
diff --git a/src/FileAttachmentField.php b/src/FileAttachmentField.php
index be368f7..ddea293 100644
--- a/src/FileAttachmentField.php
+++ b/src/FileAttachmentField.php
@@ -1139,7 +1139,7 @@ public function AttachedFiles()
     public function RootThumbnailsDir()
     {
         return $this->getSetting('thumbnailsDir') ?:
-            ModuleResourceLoader::singleton()->resolveResource('unclecheese/dropzone:images/file-icons');
+            ModuleResourceLoader::singleton()->resolveURL('unclecheese/dropzone:images/file-icons');
     }
 
     /**
diff --git a/src/FileAttachmentFieldTrack.php b/src/FileAttachmentFieldTrack.php
index 5894252..c032e9e 100644
--- a/src/FileAttachmentFieldTrack.php
+++ b/src/FileAttachmentFieldTrack.php
@@ -2,6 +2,7 @@
 
 namespace UncleCheese\Dropzone;
 
+use SilverStripe\Assets\File;
 use SilverStripe\Control\Controller;
 use SilverStripe\ORM\DataObject;
 use SilverStripe\ORM\DataObjectInterface;
@@ -20,7 +21,7 @@ class FileAttachmentFieldTrack extends DataObject
     );
 
     private static $has_one = array(
-        'File' => 'File',
+        'File' => File::class,
     );
 
     private static $table_name = 'FileAttachmentFieldTrack';