diff --git a/mozilla/toolkit/content/widgets/datetimepicker.xml b/mozilla/toolkit/content/widgets/datetimepicker.xml
index 113c0be50ad..02f2f3dc8bd 100644
--- a/mozilla/toolkit/content/widgets/datetimepicker.xml
+++ b/mozilla/toolkit/content/widgets/datetimepicker.xml
@@ -1231,7 +1231,7 @@
       <xul:dropmarker class="datepicker-dropmarker"/>
       <xul:menupopup>
         <xul:datepicker anonid="grid" type="grid" class="datepicker-popupgrid"
-                        xbl:inherits="disabled,readonly"/>
+                        xbl:inherits="disabled,readonly,firstdayofweek"/>
       </xul:menupopup>
     </content>
     <implementation>