diff --git a/mistralclient/shell.py b/mistralclient/shell.py
index 9abbda60..ee99e998 100644
--- a/mistralclient/shell.py
+++ b/mistralclient/shell.py
@@ -31,6 +31,7 @@ import mistralclient.commands.v2.services
 import mistralclient.commands.v2.tasks
 import mistralclient.commands.v2.workbooks
 import mistralclient.commands.v2.workflows
+from mistralclient import exceptions as exe
 from mistralclient.openstack.common import cliutils as c
 
 from cliff import app
@@ -237,7 +238,7 @@ class MistralShell(app.App):
             '--os-username',
             action='store',
             dest='username',
-            default=c.env('OS_USERNAME', default='admin'),
+            default=c.env('OS_USERNAME'),
             help='Authentication username (Env: OS_USERNAME)'
         )
 
@@ -376,6 +377,19 @@ class MistralShell(app.App):
         if do_help or ('bash-completion' in argv):
             self.options.auth_url = None
 
+        if self.options.auth_url and not self.options.token:
+            if not self.options.username:
+                raise exe.IllegalArgumentException(
+                    ("You must provide a username "
+                     "via --os-username env[OS_USERNAME]")
+                )
+
+            if not self.options.password:
+                raise exe.IllegalArgumentException(
+                    ("You must provide a password "
+                     "via --os-password env[OS_PASSWORD]")
+                )
+
         kwargs = {
             'cert': self.options.os_cert,
             'key': self.options.os_key
diff --git a/mistralclient/tests/unit/test_shell.py b/mistralclient/tests/unit/test_shell.py
index e6b07197..026eb52b 100644
--- a/mistralclient/tests/unit/test_shell.py
+++ b/mistralclient/tests/unit/test_shell.py
@@ -84,7 +84,12 @@ class TestShell(base.BaseShellTests):
 
     @mock.patch('mistralclient.api.client.client')
     def test_auth_url(self, mock):
-        self.shell('--os-auth-url=https://127.0.0.1:35357/v3 workbook-list')
+        self.shell(
+            '--os-auth-url=https://127.0.0.1:35357/v3 '
+            '--os-username=admin '
+            '--os-password=1234 '
+            'workbook-list'
+        )
         self.assertTrue(mock.called)
         params = mock.call_args
         self.assertEqual('https://127.0.0.1:35357/v3', params[1]['auth_url'])
@@ -105,7 +110,10 @@ class TestShell(base.BaseShellTests):
 
     @mock.patch('mistralclient.api.client.client')
     def test_default_auth_url_with_os_auth_token(self, mock):
-        self.shell('--os-auth-token=abcd1234 workbook-list')
+        self.shell(
+            '--os-auth-token=abcd1234 '
+            'workbook-list'
+        )
         self.assertTrue(mock.called)
         params = mock.call_args
         self.assertEqual('http://localhost:35357/v3', params[1]['auth_url'])