diff --git a/Dockerfile b/Dockerfile
index 4d336f9..c76590e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -11,5 +11,5 @@ RUN \
   fix-permissions $CONDA_DIR && \
   fix-permissions /home/$NB_USER 
 
-CMD ["start-notebook.sh", "--NotebookApp.token=''", "--NotebookApp.base_url=$GATEWAY_URL"]
+CMD ["start-notebook.sh", "--NotebookApp.token=''", "--NotebookApp.base_url="${GATEWAY_URL}]