diff --git a/Dockerfile b/Dockerfile
index fdf3554..5dd8aff 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,13 +1,11 @@
 ARG VERSION=latest
 
-ARG pip="/opt/indico/.venv/bin/pip"
-
 FROM ghcr.io/indico/indico:$VERSION
 
 # all the installations etc can be done using the unprivileged indico user
 USER indico
 
-RUN ${pip} install git+https://github.com/WIPACrepo/indico-sso-plugin.git
+RUN /opt/indico/.venv/bin/pip install git+https://github.com/WIPACrepo/indico-sso-plugin.git
 
 ENTRYPOINT ["/opt/indico/docker_entrypoint.sh"]
 EXPOSE 59999