diff --git a/downloader/downloader.go b/downloader/downloader.go
index 71f914426..9a44c55f2 100644
--- a/downloader/downloader.go
+++ b/downloader/downloader.go
@@ -630,8 +630,8 @@ func (downloader *Downloader) Download(data *types.Data) error {
 	}
 
 	fmt.Printf("Merging video parts into %s\n", mergedFilePath)
-	if stream.Ext == "mp4" {
-		return utils.MergeToMP4(parts, mergedFilePath, title)
+	if stream.Ext != "mp4" || data.Site == "YouTube youtube.com" {
+		return utils.MergeFilesWithSameExtension(parts, mergedFilePath)
 	}
-	return utils.MergeFilesWithSameExtension(parts, mergedFilePath)
+	return utils.MergeToMP4(parts, mergedFilePath, title)
 }
diff --git a/utils/ffmpeg.go b/utils/ffmpeg.go
index 6d4fdfc2c..730d186e3 100644
--- a/utils/ffmpeg.go
+++ b/utils/ffmpeg.go
@@ -26,6 +26,7 @@ func runMergeCmd(cmd *exec.Cmd, paths []string, mergeFilePath string) error {
 }
 
 // MergeFilesWithSameExtension merges files that have the same extension into one.
+// Can also handle merging audio and video.
 func MergeFilesWithSameExtension(paths []string, mergedFilePath string) error {
 	cmds := []string{
 		"-y",