Index: chrome/content/ui/filters-filteractions.js
===================================================================
--- a/chrome/content/ui/filters-filteractions.js
+++ b/chrome/content/ui/filters-filteractions.js
@@ -21,21 +21,17 @@
  */
 var FilterActions =
 {
   /**
    * Initializes filter actions.
    */
   init: function()
   {
-    let me = this;
-    this.treeElement.parentNode.addEventListener("keypress", function(event)
-    {
-      me.keyPress(event);
-    }, true);
+    this.treeElement.parentNode.addEventListener("keydown", this.keyDown.bind(this), true);
     this.treeElement.view = FilterView;
 
     // Work around https://bugzilla.mozilla.org/show_bug.cgi?id=777832, don't
     // allow the tree to receive keypress/keydown events triggered by cursor
     // keys pressed in the editor, it will call preventDefault() on them.
     let propagationStopper = function(event)
     {
       if (event.keyCode >= event.DOM_VK_PAGE_UP && event.keyCode <= event.DOM_VK_DOWN)
@@ -368,17 +364,17 @@ var FilterActions =
       E("tooltip-additional").textContent = Utils.getString("filter_regexp_tooltip");
     else
       E("tooltip-additional").hidden = true;
   },
 
   /**
    * Called whenever a key is pressed on the list.
    */
-  keyPress: function(/**Event*/ event)
+  keyDown: function(/**Event*/ event)
   {
     if (event.target != E("filtersTree"))
       return;
 
     let modifiers = 0;
     if (event.altKey)
       modifiers |= SubscriptionActions._altMask;
     if (event.ctrlKey)