diff --git a/addons/account/account_invoice.py b/addons/account/account_invoice.py
index aefa91aa3da..6625cc5493a 100644
--- a/addons/account/account_invoice.py
+++ b/addons/account/account_invoice.py
@@ -781,6 +781,9 @@ class account_invoice(models.Model):
                     line2[tmp]['tax_amount'] += l['tax_amount']
                     line2[tmp]['amount_currency'] += l['amount_currency']
                     line2[tmp]['analytic_lines'] += l['analytic_lines']
+                    qty = l.get('quantity')
+                    if qty:
+                        line2[tmp]['quantity'] = line2[tmp].get('quantity', 0.0) + qty
                 else:
                     line2[tmp] = l
             line = []