diff --git a/vc_dummy/indico_vc_dummy/plugin.py b/vc_dummy/indico_vc_dummy/plugin.py
index 37b355f..3600a87 100644
--- a/vc_dummy/indico_vc_dummy/plugin.py
+++ b/vc_dummy/indico_vc_dummy/plugin.py
@@ -21,7 +21,7 @@ from wtforms.fields.core import BooleanField
 
 from indico.core.plugins import IndicoPlugin, url_for_plugin, IndicoPluginBlueprint
 from indico.modules.vc import VCPluginMixin
-from indico.modules.vc.forms import VCRoomFormBase
+from indico.modules.vc.forms import VCRoomFormBase, VCRoomAttachFormBase
 from indico.web.forms.widgets import SwitchWidget
 
 
@@ -31,6 +31,12 @@ class VCRoomForm(VCRoomFormBase):
                                       description="Yes. It doesn't make any sense.")
 
 
+class VCRoomAttachForm(VCRoomAttachFormBase):
+    show_phone_numbers = BooleanField('What is your favorite color?',
+                                      widget=SwitchWidget(),
+                                      description="Yes. It doesn't make any sense.")
+
+
 class DummyPlugin(VCPluginMixin, IndicoPlugin):
     """Dummy
 
@@ -38,6 +44,7 @@ class DummyPlugin(VCPluginMixin, IndicoPlugin):
     """
     configurable = True
     vc_room_form = VCRoomForm
+    vc_room_attach_form = VCRoomAttachForm
     friendly_name = "Dummy"
 
     @property