diff --git a/Dockerfile b/Dockerfile
index ffad931e21c9643d8051d0432bb7b3435cb3f39d..385f4aafc30207e7e02e5e78e2689df0e48af86a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -89,8 +89,8 @@ RUN chown -R www-data:www-data \
 USER 33:33
 
 # Additional steps
+ONBUILD ARG APPS
 ONBUILD USER 0:0
-ONBUILD ARG APPS=""
 ONBUILD RUN set -e; \
             if [ -n "$APPS" ]; then \
                 eatmydata pip install $APPS; \