diff --git a/dodo.py b/dodo.py
index 4962b9e..52fc71e 100644
--- a/dodo.py
+++ b/dodo.py
@@ -1,5 +1,6 @@
 import subprocess
 import os
+import sys
 
 from doit.tools import LongRunning
 
@@ -104,18 +105,28 @@ def task_up():
     }
 
 
-def restart(*containers):
-    '''This actually restart the container(s).'''
+def _get_valid_services():
     srv = subprocess.check_output((COMPOSE + ' config --services').split())
-    services = srv.decode('utf-8').strip().split()
-    for container in containers:
-        if container not in services:
-            raise ValueError("%s is not among the services %r" % (container, services))
-        subprocess.check_call((COMPOSE + 'restart %s' % container).split())
+    return srv.decode('utf-8').strip().split()
+
+
+def restart(services):
+    '''This actually restart the container(s).'''
+    valid = _get_valid_services()
+    err = False
+    for service in services:
+        if service not in valid:
+            print('ERROR: invalid service %s' % service, file=sys.stderr)
+            err = True
+    if err or not services:
+        print('Valid services are: ' + ', '.join(valid), file=sys.stderr)
+        return False
+    for service in services:
+        subprocess.check_call((COMPOSE + 'restart %s' % service).split())
     return True
 
 
-def task_restart(*containers):
+def task_restart():
     '''Restarts a container specified via commandline.'''
     return {
         'params': [{'name': 'services',
@@ -124,7 +135,7 @@ def task_restart(*containers):
                     'type': list,
                     'default': [],
                     'help': "the list of services to be restarted"}],
-        'actions': [(restart, containers)],
+        'actions': [(restart, )],
     }