diff --git a/arm64v8.dockerfile b/arm64v8.dockerfile
index 1996727..5dcedb1 100644
--- a/arm64v8.dockerfile
+++ b/arm64v8.dockerfile
@@ -42,6 +42,7 @@ ENV videoFormat="bestvideo*+bestaudio/best"
 ENV scriptInterval=15m
 ENV videoDownloadTag=""
 ENV retryNotFound=90
+ENV videoContainer=mkv
 
 RUN \
 	echo "*** install packages ***" && \