diff --git a/shopfloor/services/cluster_picking.py b/shopfloor/services/cluster_picking.py
index 881b56931e..e40d981491 100644
--- a/shopfloor/services/cluster_picking.py
+++ b/shopfloor/services/cluster_picking.py
@@ -601,7 +601,12 @@ def scan_destination_pack(self, picking_batch_id, move_line_id, barcode, quantit
             # contained less items than expected)
             remaining = move_line.product_uom_qty - quantity
             new_line = move_line.copy({"product_uom_qty": remaining, "qty_done": 0})
-            move_line.product_uom_qty = quantity
+            # if we didn't bypass reservation update, the quant reservation
+            # would be reduced as much as the deduced quantity, which is wrong
+            # as we only moved the quantity to a new move line
+            move_line.with_context(
+                bypass_reservation_update=True
+            ).product_uom_qty = quantity
 
         search = self.actions_for("search")
         bin_package = search.package_from_scan(barcode)
diff --git a/shopfloor/tests/test_cluster_picking_scan.py b/shopfloor/tests/test_cluster_picking_scan.py
index b67471d560..11909cccf0 100644
--- a/shopfloor/tests/test_cluster_picking_scan.py
+++ b/shopfloor/tests/test_cluster_picking_scan.py
@@ -467,6 +467,15 @@ def test_scan_destination_pack_quantity_more(self):
     def test_scan_destination_pack_quantity_less(self):
         """Pick less units than expected"""
         line = self.one_line_picking.move_line_ids
+        quant = self.env["stock.quant"].search(
+            [
+                ("location_id", "=", line.location_id.id),
+                ("product_id", "=", line.product_id.id),
+            ]
+        )
+        quant.ensure_one()
+        self.assertRecordValues(quant, [{"quantity": 40.0, "reserved_quantity": 20.0}])
+
         # when we pick less quantity than expected, the line is split
         # and the user is proposed to pick the next line for the remaining
         # quantity
@@ -479,16 +488,7 @@ def test_scan_destination_pack_quantity_less(self):
                 "quantity": line.product_uom_qty - 3,
             },
         )
-
-        self.assertRecordValues(
-            line,
-            [{"qty_done": 7, "result_package_id": self.bin1.id, "product_uom_qty": 7}],
-        )
         new_line = self.one_line_picking.move_line_ids - line
-        self.assertRecordValues(
-            new_line,
-            [{"qty_done": 0, "result_package_id": False, "product_uom_qty": 3}],
-        )
 
         self.assert_response(
             response,
@@ -502,6 +502,17 @@ def test_scan_destination_pack_quantity_less(self):
             },
         )
 
+        self.assertRecordValues(
+            line,
+            [{"qty_done": 7, "result_package_id": self.bin1.id, "product_uom_qty": 7}],
+        )
+        self.assertRecordValues(
+            new_line,
+            [{"qty_done": 0, "result_package_id": False, "product_uom_qty": 3}],
+        )
+        # the reserved quantity on the quant must stay the same
+        self.assertRecordValues(quant, [{"quantity": 40.0, "reserved_quantity": 20.0}])
+
     def test_scan_destination_pack_zero_check(self):
         """Location will be emptied, have to go to zero check"""
         line = self.one_line_picking.move_line_ids