diff --git a/addons/account_payment/controllers/payment.py b/addons/account_payment/controllers/payment.py
index ecd331d2d9c..7427d768dad 100644
--- a/addons/account_payment/controllers/payment.py
+++ b/addons/account_payment/controllers/payment.py
@@ -1,9 +1,8 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from werkzeug import url_encode
-
 from odoo import http, _
+from odoo.addons.portal.controllers.portal import _build_url_w_params
 from odoo.http import request, route
 
 
@@ -68,7 +67,7 @@ class PaymentPortal(http.Controller):
         invoice_sudo = request.env['account.invoice'].sudo().browse(invoice_id)
         if not invoice_sudo:
             params['error'] = 'pay_invoice_invalid_doc'
-            return request.redirect('%s?%s' % (error_url, url_encode(params)))
+            return request.redirect(_build_url_w_params(error_url, params))
 
         try:
             token = request.env['payment.token'].sudo().browse(int(pm_id))
@@ -76,7 +75,7 @@ class PaymentPortal(http.Controller):
             token = False
         if not token:
             params['error'] = 'pay_invoice_invalid_token'
-            return request.redirect('%s?%s' % (error_url, url_encode(params)))
+            return request.redirect(_build_url_w_params(error_url, params))
 
         # find an existing tx or create a new one
         tx = request.env['payment.transaction'].sudo()._check_or_create_invoice_tx(
@@ -97,7 +96,7 @@ class PaymentPortal(http.Controller):
         res = tx.confirm_invoice_token()
         if res is not True:
             params['error'] = res
-            return request.redirect('%s?%s' % (error_url, url_encode(params)))
+            return request.redirect(_build_url_w_params(error_url, params))
 
         params['success'] = 'pay_invoice'
-        return request.redirect('%s?%s' % (success_url, url_encode(params)))
+        return request.redirect(_build_url_w_params(success_url, params))
diff --git a/addons/portal/controllers/portal.py b/addons/portal/controllers/portal.py
index 14edafba7b3..e107517b210 100644
--- a/addons/portal/controllers/portal.py
+++ b/addons/portal/controllers/portal.py
@@ -83,6 +83,24 @@ def get_records_pager(ids, current):
     return {}
 
 
+def _build_url_w_params(url_string, query_params, remove_duplicates=True):
+    """ Rebuild a string url based on url_string and correctly compute query parameters
+    using those present in the url and those given by query_params. Having duplicates in
+    the final url is optional. For example:
+
+     * url_string = '/my?foo=bar&error=pay'
+     * query_params = {'foo': 'bar2', 'alice': 'bob'}
+     * if remove duplicates: result = '/my?foo=bar2&error=pay&alice=bob'
+     * else: result = '/my?foo=bar&foo=bar2&error=pay&alice=bob'
+    """
+    url = urls.url_parse(url_string)
+    url_params = url.decode_query()
+    if remove_duplicates:  # convert to standard dict instead of werkzeug multidict to remove duplicates automatically
+        url_params = url_params.to_dict()
+    url_params.update(query_params)
+    return url.replace(query=urls.url_encode(url_params)).to_url()
+
+
 class CustomerPortal(Controller):
 
     MANDATORY_BILLING_FIELDS = ["name", "phone", "email", "street", "city", "country_id"]
diff --git a/addons/sale_payment/controllers/payment.py b/addons/sale_payment/controllers/payment.py
index 7487b1b6ba9..5183e8c58e1 100644
--- a/addons/sale_payment/controllers/payment.py
+++ b/addons/sale_payment/controllers/payment.py
@@ -1,9 +1,8 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from werkzeug import url_encode
-
 from odoo import http, _
+from odoo.addons.portal.controllers.portal import _build_url_w_params
 from odoo.http import request, route
 
 
@@ -68,7 +67,7 @@ class PaymentPortal(http.Controller):
         order_sudo = request.env['sale.order'].sudo().browse(order_id)
         if not order_sudo:
             params['error'] = 'pay_sale_invalid_doc'
-            return request.redirect('%s?%s' % (error_url, url_encode(params)))
+            return request.redirect(_build_url_w_params(error_url, params))
 
         try:
             token = request.env['payment.token'].sudo().browse(int(pm_id))
@@ -76,7 +75,7 @@ class PaymentPortal(http.Controller):
             token = False
         if not token:
             params['error'] = 'pay_sale_invalid_token'
-            return request.redirect('%s?%s' % (error_url, url_encode(params)))
+            return request.redirect(_build_url_w_params(error_url, params))
 
         # find an existing tx or create a new one
         tx = request.env['payment.transaction'].sudo()._check_or_create_sale_tx(
@@ -97,7 +96,7 @@ class PaymentPortal(http.Controller):
         res = tx.confirm_sale_token()
         if res is not True:
             params['error'] = res
-            return request.redirect('%s?%s' % (error_url, url_encode(params)))
+            return request.redirect(_build_url_w_params(error_url, params))
 
         params['success'] = 'pay_sale'
-        return request.redirect('%s?%s' % (success_url, url_encode(params)))
+        return request.redirect(_build_url_w_params(success_url, params))