diff --git a/get_peertube_videos/get_peertube_videos.py b/get_peertube_videos/get_peertube_videos.py
index 1d3391e..d608fc9 100644
--- a/get_peertube_videos/get_peertube_videos.py
+++ b/get_peertube_videos/get_peertube_videos.py
@@ -143,7 +143,7 @@ class GetPeertubeVideos:
                         sel_thumb = thumb
                 if 'url' in sel_thumb:
                     split_url = sel_thumb['url'].split('.')
-                    thumb_file_name = file_name.replace(file_extension, split_url[len(split_url)-1])
+                    thumb_file_name = file_name.replace(file_extension, f".{split_url[len(split_url)-1]}")
                     full_thumb_file_name = os.path.join(self.config['download_dir'], thumb_file_name)
                     result = self.session.get(sel_thumb['url'])
                     thumb_bytes = result.content