diff --git a/addons/stock/stock.py b/addons/stock/stock.py
index 9016344abb2..1606a7e4936 100644
--- a/addons/stock/stock.py
+++ b/addons/stock/stock.py
@@ -942,6 +942,12 @@ class stock_picking(osv.osv):
         return super(stock_picking, self).unlink(cr, uid, ids, context=context)
 
     def write(self, cr, uid, ids, vals, context=None):
+        if vals.get('move_lines') and not vals.get('pack_operation_ids'):
+            # pack operations are directly dependant of move lines, it needs to be recomputed
+            pack_operation_obj = self.pool['stock.pack.operation']
+            existing_package_ids = pack_operation_obj.search(cr, uid, [('picking_id', 'in', ids)], context=context)
+            if existing_package_ids:
+                pack_operation_obj.unlink(cr, uid, existing_package_ids, context)
         res = super(stock_picking, self).write(cr, uid, ids, vals, context=context)
         #if we changed the move lines or the pack operations, we need to recompute the remaining quantities of both
         if 'move_lines' in vals or 'pack_operation_ids' in vals:
diff --git a/addons/stock/wizard/stock_transfer_details.py b/addons/stock/wizard/stock_transfer_details.py
index ed03413f5fa..17f302f6317 100644
--- a/addons/stock/wizard/stock_transfer_details.py
+++ b/addons/stock/wizard/stock_transfer_details.py
@@ -48,7 +48,8 @@ class stock_transfer_details(models.TransientModel):
         picking = self.pool.get('stock.picking').browse(cr, uid, picking_id, context=context)
         items = []
         packs = []
-        picking.do_prepare_partial()
+        if not picking.pack_operation_ids:
+            picking.do_prepare_partial()
         for op in picking.pack_operation_ids:
             item = {
                 'packop_id': op.id,