diff --git a/chat/indico_chat/controllers/management.py b/chat/indico_chat/controllers/management.py
index b16dc85..7bcb6a5 100644
--- a/chat/indico_chat/controllers/management.py
+++ b/chat/indico_chat/controllers/management.py
@@ -16,7 +16,7 @@
 
 from __future__ import unicode_literals
 
-from flask import session, request, flash, redirect, jsonify
+from flask import session, flash, redirect, jsonify
 from flask_pluginengine import current_plugin
 
 from indico.core.db import db
@@ -29,25 +29,34 @@ from indico.web.forms.base import FormDefaults
 
 from indico_chat import _
 from indico_chat.controllers.base import RHChatManageEventBase, RHEventChatroomMixin
-from indico_chat.forms import AddChatroomForm, EditChatroomForm
+from indico_chat.forms import AddChatroomForm, EditChatroomForm, AttachChatroomForm
 from indico_chat.models.chatrooms import ChatroomEventAssociation, Chatroom
 from indico_chat.notifications import notify_created, notify_attached, notify_modified, notify_deleted
 from indico_chat.views import WPChatEventMgmt
 from indico_chat.xmpp import create_room, update_room, get_room_config, room_exists
 
 
-class RHChatManageEvent(RHChatManageEventBase):
+class AttachChatroomMixin:
+    def _get_attach_form(self):
+        form = AttachChatroomForm()
+        form.chatroom.query = Chatroom.find(Chatroom.created_by_user == session.user,
+                                            ~Chatroom.events.any(ChatroomEventAssociation.event_id == self.event_id))
+        return form
+
+
+class RHChatManageEvent(AttachChatroomMixin, RHChatManageEventBase):
     """Lists the chatrooms of an event"""
 
     def _process(self):
         chatrooms = ChatroomEventAssociation.find_for_event(self.event, include_hidden=True,
                                                             _eager='chatroom.events').all()
-        chatroom_filter = (~Chatroom.id.in_(x.chatroom_id for x in chatrooms)) if chatrooms else True
-        available_chatrooms = Chatroom.find_all(Chatroom.created_by_user == session.user, chatroom_filter)
         logs_enabled = current_plugin.settings.get('log_url')
+        attach_form = self._get_attach_form()
+        if not attach_form.chatroom._get_object_list():
+            attach_form = None
         return WPChatEventMgmt.render_template('manage_event.html', self._conf, event_chatrooms=chatrooms,
                                                event=self.event, chat_links=current_plugin.settings.get('chat_links'),
-                                               available_chatrooms=available_chatrooms, logs_enabled=logs_enabled)
+                                               logs_enabled=logs_enabled, attach_form=attach_form)
 
 
 class RHChatManageEventModify(RHEventChatroomMixin, RHChatManageEventBase):
@@ -122,18 +131,19 @@ class RHChatManageEventCreate(RHChatManageEventBase):
         return WPChatEventMgmt.render_template('manage_event_edit.html', self._conf, form=form, event=self.event)
 
 
-class RHChatManageEventAttach(RHChatManageEventBase):
+class RHChatManageEventAttach(AttachChatroomMixin, RHChatManageEventBase):
     """Attaches an existing chatroom to an event"""
 
     def _checkParams(self, params):
         RHChatManageEventBase._checkParams(self, params)
-        self.chatroom = Chatroom.find_one(id=request.form['chatroom_id'])
 
     def _process(self):
-        event_chatroom = ChatroomEventAssociation(event_id=self.event_id, chatroom=self.chatroom)
-        db.session.add(event_chatroom)
-        notify_attached(self.chatroom, self.event, session.user)
-        flash(_('Chatroom added'), 'success')
+        form = self._get_attach_form()
+        if form.validate_on_submit():
+            event_chatroom = ChatroomEventAssociation(event_id=self.event_id, chatroom=form.chatroom.data)
+            db.session.add(event_chatroom)
+            notify_attached(form.chatroom.data, self.event, session.user)
+            flash(_('Chatroom added'), 'success')
         return redirect(url_for_plugin('.manage_rooms', self.event))
 
 
diff --git a/chat/indico_chat/forms.py b/chat/indico_chat/forms.py
index 8eb9070..b6bde1b 100644
--- a/chat/indico_chat/forms.py
+++ b/chat/indico_chat/forms.py
@@ -17,6 +17,7 @@
 from __future__ import unicode_literals
 
 from flask_pluginengine import current_plugin
+from wtforms.ext.sqlalchemy.fields import QuerySelectField
 from wtforms.fields.core import BooleanField
 from wtforms.fields.simple import StringField, TextAreaField
 from wtforms.validators import DataRequired, ValidationError
@@ -29,6 +30,10 @@ from indico_chat.models.chatrooms import Chatroom
 from indico_chat.xmpp import generate_jid, room_exists
 
 
+class AttachChatroomForm(IndicoForm):
+    chatroom = QuerySelectField(_('Available chatrooms'), [DataRequired()], get_label='name')
+
+
 class EditChatroomForm(IndicoForm):
     event_specific_fields = {'hidden', 'show_password'}
 
diff --git a/chat/indico_chat/templates/manage_event.html b/chat/indico_chat/templates/manage_event.html
index 01ea3c6..b952ebe 100644
--- a/chat/indico_chat/templates/manage_event.html
+++ b/chat/indico_chat/templates/manage_event.html
@@ -91,22 +91,13 @@
         <a class="i-button bottom i-form-button icon-plus" href="{{ url_for_plugin('.manage_rooms_create', event) }}">{% trans %}Create new room{% endtrans %}</a>
     </div>
 
-    {% if available_chatrooms %}
+    {% if attach_form %}
         <div>
             <h2>{% trans %}Add existing chat room{% endtrans %}</h2>
             <div>
-                {{ form_header(action=url_for_plugin('.manage_rooms_attach', event), method='post') }}
-                <div class="form-group">
-                    <div class="form-label form-block form-label-middle">{% trans %}Available chatrooms{% endtrans %}</div>
-                    <div class="form-field form-block">
-                        <select name="chatroom_id">
-                            {% for chatroom in available_chatrooms -%}
-                                <option value="{{ chatroom.id }}">{{ chatroom.name }}</option>
-                            {% endfor %}
-                        </select>
-                    </div>
-                </div>
-                {% call form_footer() %}
+                {{ form_header(attach_form, action=url_for_plugin('.manage_rooms_attach', event)) }}
+                {{ form_row(attach_form.chatroom) }}
+                {% call form_footer(attach_form) %}
                     <input class="i-button big highlight" type="submit" value="{% trans %}Attach existing room{% endtrans %}">
                 {% endcall %}
             </div>
diff --git a/chat/indico_chat/templates/manage_event_edit.html b/chat/indico_chat/templates/manage_event_edit.html
index 5c72f75..e96948d 100644
--- a/chat/indico_chat/templates/manage_event_edit.html
+++ b/chat/indico_chat/templates/manage_event_edit.html
@@ -13,7 +13,7 @@
 {% endblock %}
 
 {% block content %}
-    {{ form_header(id='chatroom-form') }}
+    {{ form_header(form, id='chatroom-form') }}
 
     {% call form_fieldset(legend='Chatroom settings') %}
         {{ form_rows(form, skip=form.event_specific_fields) }}
@@ -23,8 +23,8 @@
         {{ form_rows(form, fields=form.event_specific_fields) }}
     {% endcall %}
 
-    {% call form_footer() %}
-        <input class="i-button big highlight" type="submit" value="{% trans %}Save{% endtrans %}">
+    {% call form_footer(form) %}
+        <input class="i-button big highlight" type="submit" value="{% trans %}Save{% endtrans %}" data-disabled-until-change>
         <a href="{{ url_for_plugin('.manage_rooms', event) }}" class="i-button big">{% trans %}Cancel{% endtrans %}</a>
     {% endcall %}