--- a/toolkit/locales/en-US/chrome/mozapps/handling/handling.dtd
+++ b/toolkit/locales/en-US/chrome/mozapps/handling/handling.dtd
@@ -1,5 +1,5 @@
-<!ENTITY window.width "320">
-<!ENTITY window.height "250">
+<!ENTITY window.emWidth "26em">
+<!ENTITY window.emHeight "26em">
 <!ENTITY ChooseApp.description "Choose an Application">
 <!ENTITY ChooseApp.label "Choose...">
 <!ENTITY ChooseApp.accessKey "C">

--- a/toolkit/mozapps/handling/content/dialog.xul
+++ b/toolkit/mozapps/handling/content/dialog.xul
@@ -39,18 +39,18 @@
    -
    - ***** END LICENSE BLOCK ***** -->
 
 <!DOCTYPE dialog SYSTEM "chrome://mozapps/locale/handling/handling.dtd">
 
 <dialog id="handling"
         ondialogaccept="return dialog.onAccept();"
         onload="dialog.initialize();"
-        width="&window.width;" height="&window.height;"
-        persist="width height screenX screenY sizemode"
+        style="min-width: &window.emWidth;; min-height: &window.emHeight;;"
+        persist="width height screenX screenY"
         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 
   <script src="chrome://mozapps/content/handling/dialog.js" type="application/javascript"/>
 
   <stringbundleset id="strings">
     <stringbundle id="base-strings"
                   src="chrome://mozapps/locale/handling/handling.properties"/>
   </stringbundleset>