diff --git a/src/xproto.xml b/src/xproto.xml
index 69f3c8a..5a056e8 100644
--- a/src/xproto.xml
+++ b/src/xproto.xml
@@ -866,6 +866,8 @@ authorization from the authors.
   <request name="ConfigureWindow" opcode="12">
     <pad bytes="1" />
     <field type="WINDOW" name="window" />
+    <field type="CARD16" name="value_mask" />
+    <pad bytes="2" />
     <valueparam value-mask-type="CARD16"
                 value-mask-name="value_mask"
                 value-list-name="value_list" />