diff --git a/amd64.dockerfile b/amd64.dockerfile
index e0a1e2f..9e22feb 100644
--- a/amd64.dockerfile
+++ b/amd64.dockerfile
@@ -32,6 +32,7 @@ ENV scriptInterval=15m
 ENV videoFormat="bestvideo*+bestaudio/best"
 ENV videoDownloadTag=""
 ENV retryNotFound=90
+ENV videoContainer=mkv
 
 RUN \
 	echo "*** install packages ***" && \