diff --git a/Dockerfile.jupyterhub b/Dockerfile.jupyterhub
index b0371f5..16d9bf0 100644
--- a/Dockerfile.jupyterhub
+++ b/Dockerfile.jupyterhub
@@ -6,7 +6,7 @@ FROM jupyterhub/jupyterhub-onbuild:0.6.1
 RUN /opt/conda/bin/pip install \
     jupyterhub==0.6.* \
     oauthenticator==0.4.* \
-    dockerspawner==0.3.*
+    dockerspawner==0.4.*
 
 # Copy TLS certificate and key
 ENV SSL_CERT /srv/jupyterhub/secrets/jupyterhub.crt
diff --git a/README.md b/README.md
index 9b03755..dfdfeda 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ This deployment is **NOT** intended for a production environment.
 ## Prerequisites
 
 * This deployment uses Docker for all the things, via  [Docker Compose](https://docs.docker.com/compose/overview/).
-  It requires [Docker Toolbox](https://www.docker.com/products/docker-toolbox) 1.11.0 or higher.
+  It requires [Docker Engine](https://docs.docker.com/engine) 1.12.0 or higher.
   See the [installation instructions](https://docs.docker.com/engine/installation/) for your environment.
 * This example configures JupyterHub for HTTPS connections (the default).
    As such, you must provide TLS certificate chain and key files to the JupyterHub server.
diff --git a/jupyterhub_config.py b/jupyterhub_config.py
index 026698a..84dbce5 100644
--- a/jupyterhub_config.py
+++ b/jupyterhub_config.py
@@ -27,7 +27,6 @@ c.DockerSpawner.use_internal_ip = True
 c.DockerSpawner.network_name = network_name
 # Pass the network name as argument to spawned containers
 c.DockerSpawner.extra_host_config = { 'network_mode': network_name }
-c.DockerSpawner.extra_start_kwargs = { 'network_mode': network_name }
 # Explicitly set notebook directory because we'll be mounting a host volume to
 # it.  Most jupyter/docker-stacks *-notebook images run the Notebook server as
 # user `jovyan`, and set the notebook directory to `/home/jovyan/work`.