diff --git a/internal/db_channel.go b/internal/db_channel.go
index f9ef612..45f7ae5 100644
--- a/internal/db_channel.go
+++ b/internal/db_channel.go
@@ -59,7 +59,7 @@ func NewDBChannel(uuid int64, username, title string) *DBChannel {
 }
 
 func (c *DBChannel) Asset(assetID int64, ext string) string {
-	assetFile := fmt.Sprintf("%d/%d.%s", c.UUID, assetID, strings.Trim(ext, "."))
+	assetFile := fmt.Sprintf("%d/%d.%s", c.UUID, assetID, strings.ToLower(strings.Trim(ext, ".")))
 	assetFile = filepath.Join(config.C.Output, assetFile)
 
 	// if file dir not exists then create it