diff --git a/hobo/multitenant/settings_loaders.py b/hobo/multitenant/settings_loaders.py
index 2536ba3..1ff981e 100644
--- a/hobo/multitenant/settings_loaders.py
+++ b/hobo/multitenant/settings_loaders.py
@@ -141,6 +141,7 @@ class TemplateVars(FileBaseSettingsLoader):
                 if 'portal-user' in service.get('template_name', ''):
                     variables['portal_user_url'] = service.get('base_url')
                     variables['portal_user_title'] = service.get('title')
+                    variables['portal_user_slug'] = service.get('slug')
 
             if service.get('service-id') == 'authentic':
                 variables['idp_url'] = service.get('base_url')
@@ -157,8 +158,14 @@ class TemplateVars(FileBaseSettingsLoader):
             if 'portal-agent' in service.get('template_name', ''):
                 variables['is_portal_agent'] = True
 
-        if 'portal_user_url' in variables and 'idp_registration_url' in variables:
-            variables['idp_registration_url'] += '?%s' % urlencode({'next': variables['portal_user_url']})
+        if 'idp_registration_url' in variables:
+            params = {}
+            if 'portal_user_url' in variables:
+                params['next'] = variables['portal_user_url']
+            if 'portal_user_slug' in variables:
+                params['service'] = variables['portal_user_slug']
+            if params:
+                variables['idp_registration_url'] += '?%s' % urlencode(params)
 
         if getattr(settings, 'HOBO_MANAGER_HOMEPAGE_TITLE_VAR', None):
             variables['manager_homepage_title'] = \
diff --git a/tests/test_settings_loaders.py b/tests/test_settings_loaders.py
index 0d49dc4..0324b32 100644
--- a/tests/test_settings_loaders.py
+++ b/tests/test_settings_loaders.py
@@ -143,3 +143,20 @@ def test_sms_update_settings_from_path(tmpdir):
     loader.update_settings_from_path(tenant_settings, path)
     assert tenant_settings.SMS_URL == 'https://example.com/send/'
     assert tenant_settings.SMS_SENDER == 'Sender'
+
+
+def test_get_hobo_json_variables(tmpdir):
+    a = Authentic(title='bar', slug='bar', base_url='http://bar.example.net')
+    a.save()
+    c = Combo(title='combo', slug='portal', base_url='http://portal.example.net', template_name='portal-user')
+    c.save()
+
+    loader = TemplateVars()
+    env = get_hobo_json()
+
+    variables = loader.get_hobo_json_variables(env)
+
+    url = variables['idp_registration_url']
+    assert url.startswith('http://bar.example.net/accounts/register/?')
+    assert 'next=http%3A%2F%2Fportal.example.net%2F' in url
+    assert 'service=portal' in url