diff --git a/src/js/plugins/previewThumbnails.js b/src/js/plugins/previewThumbnails.js
index 813bc47e..3e4b17a3 100644
--- a/src/js/plugins/previewThumbnails.js
+++ b/src/js/plugins/previewThumbnails.js
@@ -149,9 +149,11 @@ class PreviewThumbnails {
                 // If the URLs don't start with '/', then we need to set their relative path to be the location of the VTT file
                 // If the URLs do start with '/', then they obviously don't need a prefix, so it will remain blank
                 // If the thumbnail URLs start with with none of '/', 'http://' or 'https://', then we need to set their relative path to be the location of the VTT file
-                if (!thumbnail.frames[0].text.startsWith('/') &&
+                if (
+                    !thumbnail.frames[0].text.startsWith('/') &&
                     !thumbnail.frames[0].text.startsWith('http://') &&
-                    !thumbnail.frames[0].text.startsWith('https://')) {
+                    !thumbnail.frames[0].text.startsWith('https://')
+                ) {
                     thumbnail.urlPrefix = url.substring(0, url.lastIndexOf('/') + 1);
                 }
 
@@ -297,7 +299,9 @@ class PreviewThumbnails {
         this.elements.thumb.container.appendChild(timeContainer);
 
         // Inject the whole thumb
-        this.player.elements.progress.appendChild(this.elements.thumb.container);
+        if (is.element(this.player.elements.progress)) {
+            this.player.elements.progress.appendChild(this.elements.thumb.container);
+        }
 
         // Create HTML element: plyr__preview-scrubbing-container
         this.elements.scrubbing.container = createElement('div', {