diff --git a/base_user_role/models/role.py b/base_user_role/models/role.py
index 109a41692..14cfb920e 100644
--- a/base_user_role/models/role.py
+++ b/base_user_role/models/role.py
@@ -88,6 +88,13 @@ class ResUsersRoleLine(models.Model):
     date_from = fields.Date("From")
     date_to = fields.Date("To")
     is_enabled = fields.Boolean("Enabled", compute="_compute_is_enabled")
+    _sql_constraints = [
+        (
+            "user_role_uniq",
+            "unique (user_id,role_id)",
+            "Roles can be assigned to a user only once at a time",
+        )
+    ]
 
     @api.depends("date_from", "date_to")
     def _compute_is_enabled(self):
diff --git a/base_user_role/readme/CONTRIBUTORS.rst b/base_user_role/readme/CONTRIBUTORS.rst
index b0539e398..b34cf97aa 100644
--- a/base_user_role/readme/CONTRIBUTORS.rst
+++ b/base_user_role/readme/CONTRIBUTORS.rst
@@ -3,5 +3,6 @@
 * Jean-Charles Drubay <jc@komit-consulting.com> (https://komit-consulting.com)
 * Alan Ramos <alan.ramos@jarsa.com.mx> (https://www.jarsa.com.mx)
 * Harald Panten <harald.panten@sygel.es>
+* Kevin Khao <kevin.khao@akretion.com>
 
 Do not contact contributors directly about support or help with technical issues.
diff --git a/base_user_role/views/user.xml b/base_user_role/views/user.xml
index 6625b414f..bf8bf1284 100644
--- a/base_user_role/views/user.xml
+++ b/base_user_role/views/user.xml
@@ -10,9 +10,13 @@
         <field name="arch" type="xml">
             <xpath expr="//notebook/page[1]" position="before">
                 <page string="Roles">
+                    <field name="role_ids" invisible="1" />
                     <field name="role_line_ids" nolabel="1">
                         <tree editable="bottom" decoration-muted="not is_enabled">
-                            <field name="role_id" />
+                            <field
+                                name="role_id"
+                                domain="[('id', 'not in', parent.role_ids)]"
+                            />
                             <field name="date_from" />
                             <field name="date_to" />
                             <field name="is_enabled" />