diff --git a/Dockerfile b/Dockerfile
index df167d0..a305409 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -6,6 +6,7 @@ CMD ["/sbin/entrypoint.sh"]
 ARG cachet_ver
 ARG archive_url
 
+ENV cachet_ver ${cachet_ver:-2.5}
 ENV archive_url https://github.com/dBildungsplattform/Cachet/archive/2.5.tar.gz
 
 ENV COMPOSER_VERSION 1.9.0