diff --git a/admin/js/plugins/dropzone/dropzone.js b/admin/js/plugins/dropzone/dropzone.js
index 27a69c98..b51cd8ce 100644
--- a/admin/js/plugins/dropzone/dropzone.js
+++ b/admin/js/plugins/dropzone/dropzone.js
@@ -913,7 +913,7 @@ function (_Emitter) {
           if (file.previewElement) {
             file.previewElement.classList.add("dz-error");
 
-            if (typeof message !== "String" && message.error) {
+            if (typeof message !== "string" && message.error) {
               message = message.error;
             }