diff --git a/Dockerfile b/Dockerfile
index 8c57257..3d56b9b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,7 +2,8 @@ FROM debian:latest
 
 LABEL Maintainer="Wolfgang Hottgenroth <woho@hottis.de>"
 LABEL ImageName="registry.gitlab.com/wolutator/base-build-env"
-RELEASETOOL_URL="https://gitlab.com/wolutator/gitlabreleaseuploader/uploads/ffc1cc36bbd7e1a56c121f51bf1b4b90/GitlabReleaseTool.zip"
+
+ARG RELEASETOOL_URL="https://gitlab.com/wolutator/gitlabreleaseuploader/uploads/ffc1cc36bbd7e1a56c121f51bf1b4b90/GitlabReleaseTool.zip"
 
 RUN \
   apt-get update && \