=== modified file 'stock/wizard/stock_partial_picking_view.xml'
--- stock/wizard/stock_partial_picking_view.xml	2011-12-30 11:06:04 +0000
+++ stock/wizard/stock_partial_picking_view.xml	2012-07-30 14:08:22 +0000
@@ -23,7 +23,7 @@
                             <field name="quantity" />
                             <field name="product_uom" />
                             <field name="tracking" invisible="1"/>
-                            <field name="prodlot_id" domain="[('product_id', '=', product_id)]" invisible="context.get('hide_tracking',False)" attrs="{'required':[('tracking','=',True)]}"/>
+                            <field name="prodlot_id" domain="[('product_id', '=', product_id)]" invisible="context.get('hide_tracking',False)" attrs="{'required':[('tracking','=',True), ('quantity', '!=', 0)]}"/>
                             <!-- Removed as this feature is not logic: price must be updated upon reception of invoice -->
                             <field name="update_cost" invisible="1"/>
                             <field name="cost"  invisible="1"/>