diff --git a/app/assets/javascripts/discourse/mixins/upload.js.es6 b/app/assets/javascripts/discourse/mixins/upload.js.es6
index a0566228044..c99e671dfd4 100644
--- a/app/assets/javascripts/discourse/mixins/upload.js.es6
+++ b/app/assets/javascripts/discourse/mixins/upload.js.es6
@@ -9,7 +9,7 @@ export default Em.Mixin.create({
   _initialize: function() {
     const $upload = this.$(),
           csrf = Discourse.Session.currentProp("csrfToken"),
-          uploadUrl = this.getWithDefault("uploadUrl", "/uploads"),
+          uploadUrl = Discourse.getURL(this.getWithDefault("uploadUrl", "/uploads")),
           reset = () => this.setProperties({ uploading: false, uploadProgress: 0});
 
     this.messageBus.subscribe("/uploads/" + this.get("type"), upload => {