diff --git a/addons/account/account_analytic_line.py b/addons/account/account_analytic_line.py
index 43bd821695d..7286229bdf0 100644
--- a/addons/account/account_analytic_line.py
+++ b/addons/account/account_analytic_line.py
@@ -80,7 +80,7 @@ class account_analytic_line(osv.osv):
         j_id = analytic_journal_obj.browse(cr, uid, journal_id, context=context)
         prod = product_obj.browse(cr, uid, prod_id, context=context)
         result = 0.0
-        if prod_id or not unit:
+        if prod_id:
             unit = prod.uom_id.id
             if j_id.type == 'purchase':
                 unit = prod.uom_po_id.id