diff --git a/trytond/ir/ui/tree.rnc b/trytond/ir/ui/tree.rnc
index a24cb8a3ee..c2974da983 100644
--- a/trytond/ir/ui/tree.rnc
+++ b/trytond/ir/ui/tree.rnc
@@ -88,6 +88,8 @@ data = element data { attlist.data, xpath* }
 attlist.data &= empty
 xpath = element xpath { attlist.xpath,
     (field
+    | prefix
+    | suffix
     | button
     | tree
     )*
diff --git a/trytond/ir/ui/tree.rng b/trytond/ir/ui/tree.rng
index 132b320efe..3fa256536f 100644
--- a/trytond/ir/ui/tree.rng
+++ b/trytond/ir/ui/tree.rng
@@ -417,6 +417,8 @@
       <zeroOrMore>
         <choice>
           <ref name="field"/>
+          <ref name="prefix"/>
+          <ref name="suffix"/>
           <ref name="button"/>
           <ref name="tree"/>
         </choice>