diff --git a/runbot/container.py b/runbot/container.py
index e8eff021..797e7c44 100644
--- a/runbot/container.py
+++ b/runbot/container.py
@@ -121,7 +121,7 @@ def docker_run(*args, **kwargs):
     return _docker_run(*args, **kwargs)
 
 
-def _docker_run(run_cmd, log_path, build_dir, container_name, image_tag='odoo:DockerDefault', exposed_ports=None, cpu_limit=None, preexec_fn=None, ro_volumes=None, env_variables=None):
+def _docker_run(run_cmd, log_path, build_dir, container_name, image_tag=False, exposed_ports=None, cpu_limit=None, preexec_fn=None, ro_volumes=None, env_variables=None):
     """Run tests in a docker container
     :param run_cmd: command string to run in container
     :param log_path: path to the logfile that will contain odoo stdout and stderr
@@ -133,6 +133,7 @@ def _docker_run(run_cmd, log_path, build_dir, container_name, image_tag='odoo:Do
     :params ro_volumes: dict of dest:source volumes to mount readonly in builddir
     :params env_variables: list of environment variables
     """
+    image_tag = image_tag or 'odoo:DockerDefault'
     container_name = sanitize_container_name(container_name)
     if isinstance(run_cmd, Command):
         cmd_object = run_cmd
diff --git a/runbot/models/host.py b/runbot/models/host.py
index f4fc8ca5..f670177f 100644
--- a/runbot/models/host.py
+++ b/runbot/models/host.py
@@ -82,7 +82,7 @@ class Host(models.Model):
             with open(os.path.join(docker_build_path, 'Dockerfile'), 'w') as Dockerfile:
                 Dockerfile.write(dockerfile.dockerfile)
             build_process = docker_build(docker_build_path, dockerfile.image_tag)
-            if build_process.returncode != 0:
+            if build_process != 0:
                 dockerfile.to_build = False
                 message = 'Dockerfile build "%s" failed on host %s' % (dockerfile.image_tag, self.name)
                 dockerfile.message_post(body=message)