diff --git a/CHANGELOG b/CHANGELOG
index 822e37383a..3458220312 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Change expand attribute into a factor
 * Allow SQL expression as value of fields
 * Allow customizing Dict keys order with a sequence field
 * Add invalid domain in DomainValidationError
diff --git a/doc/topics/views/index.rst b/doc/topics/views/index.rst
index c3a5d1b7f4..eab95bb599 100644
--- a/doc/topics/views/index.rst
+++ b/doc/topics/views/index.rst
@@ -557,10 +557,10 @@ field
 
     * ``width``: Set the width of the column.
 
-    * ``expand``: Boolean to specify if the column should be expanded to take
-      available extra space in the view. This space is shared equally among all
-      columns that have their "expand" property set to True. Resize don't work
-      if this option is enabled.
+    * ``expand``: An integer that specifies if the column should be expanded to
+      take available extra space in the view. This space is shared
+      proportionaly among all columns that have their "expand" property set.
+      Resize doesn't work if this option is enabled.
 
     * ``pre_validate``: see in common-attributes-pre_validate_.
 
diff --git a/trytond/ir/ui/tree.rnc b/trytond/ir/ui/tree.rnc
index f85383b545..818a2b1135 100644
--- a/trytond/ir/ui/tree.rnc
+++ b/trytond/ir/ui/tree.rnc
@@ -43,7 +43,7 @@ attlist.field &=
 attlist.field &=
   [ a:defaultValue = "0" ] attribute tree_invisible { text }?
 attlist.field &=
-  [ a:defaultValue = "0" ] attribute expand { "0" | "1" }?
+  [ a:defaultValue = "0" ] attribute expand { xsd:integer }?
 attlist.field &= attribute icon { text }?
 attlist.field &= attribute sum { text }?
 attlist.field &= attribute width { text }?
diff --git a/trytond/ir/ui/tree.rng b/trytond/ir/ui/tree.rng
index ac15072248..e41e6fc340 100644
--- a/trytond/ir/ui/tree.rng
+++ b/trytond/ir/ui/tree.rng
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <grammar xmlns="http://relaxng.org/ns/structure/1.0"
-         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0">
+         xmlns:a="http://relaxng.org/ns/compatibility/annotations/1.0"
+         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
   <define name="tree">
     <element>
       <name ns="">tree</name>
@@ -135,10 +136,7 @@
     <optional>
       <attribute a:defaultValue="0">
         <name ns="">expand</name>
-        <choice>
-          <value>0</value>
-          <value>1</value>
-        </choice>
+        <data type="integer"/>
       </attribute>
     </optional>
   </define>