diff --git a/addons/event_sale/models/sale_order.py b/addons/event_sale/models/sale_order.py
index 47f91ce8ac9..b3b79a3899c 100644
--- a/addons/event_sale/models/sale_order.py
+++ b/addons/event_sale/models/sale_order.py
@@ -65,6 +65,12 @@ class SaleOrderLine(models.Model):
         help="Choose an event ticket and it will automatically create a registration for this event ticket.")
     event_ok = fields.Boolean(related='product_id.event_ok', readonly=True)
 
+    @api.depends('state', 'event_id')
+    def _compute_product_uom_readonly(self):
+        event_lines = self.filtered(lambda line: line.event_id)
+        event_lines.update({'product_uom_readonly': True})
+        super(SaleOrderLine, self - event_lines)._compute_product_uom_readonly()
+
     def _update_registrations(self, confirm=True, cancel_to_draft=False, registration_data=None, mark_as_paid=False):
         """ Create or update registrations linked to a sales order line. A sale
         order line has a product_uom_qty attribute that will be the number of
diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index df7160a46f5..15fe235d7da 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -1231,6 +1231,7 @@ class SaleOrderLine(models.Model):
     product_uom_qty = fields.Float(string='Quantity', digits='Product Unit of Measure', required=True, default=1.0)
     product_uom = fields.Many2one('uom.uom', string='Unit of Measure', domain="[('category_id', '=', product_uom_category_id)]")
     product_uom_category_id = fields.Many2one(related='product_id.uom_id.category_id', readonly=True)
+    product_uom_readonly = fields.Boolean(compute='_compute_product_uom_readonly')
     product_custom_attribute_value_ids = fields.One2many('product.attribute.custom.value', 'sale_order_line_id', string="Custom Values")
 
     # M2M holding the values of product.attribute with create_variant field set to 'no_variant'
@@ -1282,6 +1283,11 @@ class SaleOrderLine(models.Model):
         ('line_section', "Section"),
         ('line_note', "Note")], default=False, help="Technical field for UX purpose.")
 
+    @api.depends('state')
+    def _compute_product_uom_readonly(self):
+        for line in self:
+            line.product_uom_readonly = line.state in ['sale', 'done', 'cancel']
+
     @api.depends('state', 'is_expense')
     def _compute_qty_delivered_method(self):
         """ Sale module compute delivered qty for product [('type', 'in', ['consu']), ('service_type', '=', 'manual')]
diff --git a/addons/sale/views/sale_views.xml b/addons/sale/views/sale_views.xml
index ddf837f97d6..124474d91a7 100644
--- a/addons/sale/views/sale_views.xml
+++ b/addons/sale/views/sale_views.xml
@@ -372,6 +372,7 @@
                                             <field name="price_total" invisible="1"/>
                                             <field name="price_tax" invisible="1"/>
                                             <field name="price_subtotal" invisible="1"/>
+                                            <field name="product_uom_readonly" invisible="1"/>
                                             <label for="product_uom_qty"/>
                                             <div class="o_row" name="ordered_qty">
                                                 <field
@@ -383,7 +384,7 @@
                                                     groups="uom.group_uom"
                                                     class="oe_no_button"
                                                     attrs="{
-                                                        'readonly': [('state', 'in', ('sale', 'done', 'cancel'))],
+                                                        'readonly': [('product_uom_readonly', '=', True)],
                                                         'required': [('display_type', '=', False)],
                                                     }"
                                                 />
@@ -523,12 +524,13 @@
                                         optional="show"
                                     />
                                     <field name="qty_to_invoice" invisible="1"/>
+                                    <field name="product_uom_readonly" invisible="1"/>
                                     <field
                                         name="product_uom"
                                         force_save="1"
                                         string="UoM"
                                         attrs="{
-                                            'readonly': [('state', 'in', ('sale','done', 'cancel'))],
+                                            'readonly': [('product_uom_readonly', '=', True)],
                                             'required': [('display_type', '=', False)],
                                         }"
                                         context="{'company_id': parent.company_id}"