diff --git a/mozilla/content/shared/public/nsXULAtomList.h b/mozilla/content/shared/public/nsXULAtomList.h
index 66f7bb34821..04fce9b6655 100644
--- a/mozilla/content/shared/public/nsXULAtomList.h
+++ b/mozilla/content/shared/public/nsXULAtomList.h
@@ -65,6 +65,7 @@ XUL_ATOM(fontpicker, "fontpicker")
 XUL_ATOM(text, "text")
 XUL_ATOM(toolbar, "toolbar")
 XUL_ATOM(toolbaritem, "toolbaritem")
+XUL_ATOM(toolbarbutton, "toolbarbutton")
 XUL_ATOM(toolbox, "toolbox")
 XUL_ATOM(image, "image")
 XUL_ATOM(validate, "validate")