diff --git a/stock_voucher/models/stock_picking.py b/stock_voucher/models/stock_picking.py
index e6ce19508..5fa292fd7 100644
--- a/stock_voucher/models/stock_picking.py
+++ b/stock_voucher/models/stock_picking.py
@@ -192,7 +192,7 @@ def _compute_declared_value(self):
                 for so_bom_line in stock_bom_lines.mapped("sale_line_id"):
                     bom = self.env["mrp.bom"]._bom_find(products=so_bom_line.product_id)[so_bom_line.product_id]
                     if bom and bom.type == "phantom":
-                        bom_moves = so_bom_line.move_ids & stock_bom_lines._origin
+                        bom_moves = so_bom_line.move_ids & stock_bom_lines
                         done_avg = []
                         picking_avg = []
                         boms, lines = bom.sudo().explode(
@@ -207,14 +207,21 @@ def _compute_declared_value(self):
                                     bom_quantity += line_data["qty"]
                             if not bom_quantity:
                                 continue
-                            rec_move = rec.move_ids.filtered(lambda m: m._origin.id == move.id)
-                            if not rec_move:
-                                continue
                             picking_avg.append(move.product_uom_qty / bom_quantity)
-                            done_avg.append(rec_move.quantity / bom_quantity)
+                            done_avg.append(move.quantity / bom_quantity)
                         if picking_avg and done_avg:
-                            picking_value += so_bom_line.price_reduce_taxexcl * (sum(picking_avg) / len(picking_avg))
-                            done_value += so_bom_line.price_reduce_taxexcl * (sum(done_avg) / len(done_avg))
+                            # In v18, we need to multiply by quantity to get the correct total value
+                            # price_reduce_taxexcl is the unit price, not the line total
+                            picking_value += (
+                                so_bom_line.price_reduce_taxexcl
+                                * so_bom_line.product_uom_qty
+                                * (sum(picking_avg) / len(picking_avg))
+                            )
+                            done_value += (
+                                so_bom_line.price_reduce_taxexcl
+                                * so_bom_line.product_uom_qty
+                                * (sum(done_avg) / len(done_avg))
+                            )
 
             declared_value = picking_value if inmediate_transfer else done_value
             if pricelist: