diff --git a/plugins/calendar/calendar_ui.js b/plugins/calendar/calendar_ui.js
index 59fa93a7..4c993307 100644
--- a/plugins/calendar/calendar_ui.js
+++ b/plugins/calendar/calendar_ui.js
@@ -1310,8 +1310,8 @@ function rcube_calendar_ui(settings)
         success: function(data) {
           $dialog.html(data);
           // resize and reposition dialog window
-          me.dialog_resize('#calendarform', $('#calendar-details').height(), $('#calendar-details').width());
           form = $('form', $('#calendarform')); // '#calendarform > form' doesn't work here
+          me.dialog_resize('#calendarform', form.height(), form.width());
           name = $('#calendar-name').prop('disabled', !calendar.editable).val(calendar.editname || calendar.name);
           color = $('#calendar-color').val(calendar.color).miniColors({ value: calendar.color });
           name.select();
@@ -1362,7 +1362,7 @@ function rcube_calendar_ui(settings)
       }).show();
 
     };
-    
+
     this.calendar_remove = function(calendar)
     {
       if (confirm(rcmail.gettext('deletecalendarconfirm', 'calendar'))) {
@@ -1371,7 +1371,7 @@ function rcube_calendar_ui(settings)
       }
       return false;
     };
-    
+
     this.calendar_destroy_source = function(id)
     {
       if (this.calendars[id]) {
@@ -1429,7 +1429,7 @@ function rcube_calendar_ui(settings)
           this.reset_quicksearch();
       }
     };
-    
+
     // reset search and get back to normal event listing
     this.reset_quicksearch = function()
     {
@@ -1454,7 +1454,7 @@ function rcube_calendar_ui(settings)
         this.search_request = this.search_query = null;
       }
     };
-    
+
     // callback if all sources have been fetched from server
     this.events_loaded = function(count)
     {
@@ -1465,17 +1465,18 @@ function rcube_calendar_ui(settings)
     // resize and reposition (center) the dialog window
     this.dialog_resize = function(id, height, width)
     {
-      height = Math.min(400, height+90);
-      width = Math.min(500, width+50);
-
       var win = $(window), w = win.width(), h = win.height();
 
+      height = Math.min(h-20, height+125);
+      width = Math.min(w-20, width+50);
+
       w = w - width < 0 ? 0 : (w - width) / 2;
       h = h - height < 0 ? 0 : (h - height) / 2;
 
       $(id).dialog('option', { height: height, width: width, position: [w, h] });
     };
 
+
     /***  startup code  ***/
 
     // create list of event sources AKA calendars
diff --git a/plugins/calendar/drivers/calendar_driver.php b/plugins/calendar/drivers/calendar_driver.php
index 29c202ef..db5ee8aa 100644
--- a/plugins/calendar/drivers/calendar_driver.php
+++ b/plugins/calendar/drivers/calendar_driver.php
@@ -305,10 +305,11 @@ abstract class calendar_driver
    *
    * @param string Request action 'form-edit|form-new'
    * @param array  Calendar properties (e.g. id, color)
+   * @param string HTML code of default edit form
    *
    * @return string HTML content of the form
    */
-  public function calendar_form($action, $calendar)
+  public function calendar_form($action, $calendar, $html)
   {
     return null;
   }
diff --git a/plugins/calendar/drivers/kolab/kolab_driver.php b/plugins/calendar/drivers/kolab/kolab_driver.php
index 20329332..1c21f56b 100644
--- a/plugins/calendar/drivers/kolab/kolab_driver.php
+++ b/plugins/calendar/drivers/kolab/kolab_driver.php
@@ -827,10 +827,11 @@ class kolab_driver extends calendar_driver
    *
    * @param string Request action 'form-edit|form-new'
    * @param array  Calendar properties (e.g. id, color)
+   * @param string HTML code of default edit form
    *
    * @return string HTML content of the form
    */
-  public function calendar_form($action, $calendar)
+  public function calendar_form($action, $calendar, $html)
   {
     // Remove any scripts/css/js
     $this->rc->output->reset();
diff --git a/plugins/calendar/lib/calendar_ui.php b/plugins/calendar/lib/calendar_ui.php
index 71aeb97d..4e7dcaf0 100644
--- a/plugins/calendar/lib/calendar_ui.php
+++ b/plugins/calendar/lib/calendar_ui.php
@@ -537,10 +537,21 @@ class calendar_ui
    */
   function calendar_editform($action, $calendar = array())
   {
-    $html = $this->calendar->driver->calendar_form($action, $calendar);
+    // compose default calendar form
+    $input_name = new html_inputfield(array('name' => 'name', 'id' => 'calendar-name', 'size' => 20));
+    $html = html::div('form-section',
+      html::label('calendar-name', $this->calendar->gettext('name')) .
+      $input_name->show($calendar['name']));
 
-    if (!$html)
-      $html = $this->rc->output->parse('calendar.calendarform', false, false);
+    $input_color = new html_inputfield(array('name' => 'color', 'id' => 'calendar-color', 'size' => 6));
+    $html .= html::div('form-section',
+      html::label('calendar-color', $this->calendar->gettext('color')) .
+      $input_color->show($calendar['color']));
+
+    $html = html::tag('form', array('action' => "#", 'method' => "get", 'id' => 'calendarpropform'), $html);
+
+    // allow driver to extend or replace the form content
+    $html = $this->calendar->driver->calendar_form($action, $calendar, $html);
 
     return $html;
   }