diff --git a/Dockerfile b/Dockerfile
index f25cff9..e771921 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,6 +3,7 @@
 ############
 
 ARG NODE_VERSION=18.16
+ARG PYTHON_VERSION=3.11-slim
 FROM node:${NODE_VERSION} AS build-ui
 
 # env setup
@@ -20,8 +21,8 @@ RUN yarn build --dest /tmp/advent22_ui/html
 # web app #
 ###########
 
-ARG PYTHON_VERSION=3.11
-FROM tiangolo/uvicorn-gunicorn:python${PYTHON_VERSION}-slim AS production
+ARG PYTHON_VERSION
+FROM tiangolo/uvicorn-gunicorn:python${PYTHON_VERSION} AS production
 
 # add prepared advent22_ui
 COPY --from=build-ui /tmp/advent22_ui /usr/local/share/advent22_ui