diff --git a/issue12702.diff b/issue12702.diff
new file mode 100644
index 0000000..de97b6c
--- /dev/null
+++ b/issue12702.diff
@@ -0,0 +1,25 @@
+diff --git a/tryton/modules/purchase/purchase.py b/tryton/modules/purchase/purchase.py
+index 0bc42b126a..9d4a6a4a20 100644
+--- a/tryton/modules/purchase/purchase.py
++++ b/tryton/modules/purchase/purchase.py
+@@ -1333,7 +1333,7 @@ class Line(sequence_ordered(), ModelSQL, ModelView):
+                 and self.product_supplier not in product_suppliers):
+             self.product_supplier = None
+
+-            self.unit_price = self.compute_unit_price()
++        self.unit_price = self.compute_unit_price()
+
+         self.amount = self.on_change_with_amount()
+
+diff --git a/tryton/modules/sale/sale.py b/tryton/modules/sale/sale.py
+index f412dbc85b..32c65db2fd 100644
+--- a/tryton/modules/sale/sale.py
++++ b/tryton/modules/sale/sale.py
+@@ -1328,7 +1328,7 @@ class SaleLine(TaxableMixin, sequence_ordered(), ModelSQL, ModelView):
+             self.unit = self.product.sale_uom
+             self.unit_digits = self.product.sale_uom.digits
+
+-            self.unit_price = self.compute_unit_price()
++        self.unit_price = self.compute_unit_price()
+
+         self.amount = self.on_change_with_amount()
diff --git a/series b/series
index cdaa264..ac15a96 100644
--- a/series
+++ b/series
@@ -81,3 +81,5 @@ strftime_format.diff # [ir] Fix problem with strftime format, reducing the time
 counterpart_party_payment_clearing.diff # [account_payment_clearing] Add the possiblity to have a party in the counterpart move when reconcile on a payment.
 
 issue12319.diff # [sale_advance_payment] Only create an advance line if the invoice dont have already one.
+
+issue12702.diff # [sale] [purchase] No compute unit_price when change the product