diff --git a/firmware-docker-build.sh b/firmware-docker-build.sh
index cb4f524..11f7ba9 100755
--- a/firmware-docker-build.sh
+++ b/firmware-docker-build.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 IMAGETAG=trezor-mcu-build
-FIRMWARETAG=v1.3.1
+FIRMWARETAG=${1:-master}
 
 docker build -t $IMAGETAG .
 docker run -t -v $(pwd):/output $IMAGETAG /bin/sh -c "\