diff --git a/wizard/change_uom.py b/wizard/change_uom.py
index 62a38c4..16a666c 100644
--- a/wizard/change_uom.py
+++ b/wizard/change_uom.py
@@ -73,13 +73,16 @@ class ProductUomChangeWizard(models.TransientModel):
         self.env.cr.execute("UPDATE product_template SET uom_id = %s WHERE id = %s", (self.new_uom_id.id, self.product_tmpl_id.id))
         
         # Also update Purchase UOM if specified
-        if self.new_uom_po_id:
-            if not self.new_uom_po_id._has_common_reference(self.product_tmpl_id.uom_po_id):
+        if self.new_uom_po_id and 'uom_po_id' in self.product_tmpl_id._fields:
+            if self.product_tmpl_id.uom_po_id and not self.new_uom_po_id._has_common_reference(self.product_tmpl_id.uom_po_id):
                  raise UserError(_("New Purchase UOM must be in the same category as the current Purchase UOM."))
             self.env.cr.execute("UPDATE product_template SET uom_po_id = %s WHERE id = %s", (self.new_uom_po_id.id, self.product_tmpl_id.id))
 
         # Invalidate cache to ensure the new value is read
-        self.product_tmpl_id.invalidate_recordset(['uom_id', 'uom_po_id'])
+        fields_to_invalidate = ['uom_id']
+        if 'uom_po_id' in self.product_tmpl_id._fields:
+            fields_to_invalidate.append('uom_po_id')
+        self.product_tmpl_id.invalidate_recordset(fields_to_invalidate)
         
         # Log note in chatter
         self.product_tmpl_id.message_post(body=f"UOM forcefully changed from {self.current_uom_id.name} to {self.new_uom_id.name} via Wizard.")