diff --git a/addons/base_import/models/base_import.py b/addons/base_import/models/base_import.py
index e970d1ca3ad..6a2f6b729bc 100644
--- a/addons/base_import/models/base_import.py
+++ b/addons/base_import/models/base_import.py
@@ -453,7 +453,7 @@ class Import(models.TransientModel):
             :rtype: (None, None) | (list(str), dict(int: list(str)))
         """
         if not options.get('headers'):
-            return None, None
+            return [], {}
 
         headers = next(rows)
         return headers, {
diff --git a/addons/base_import/tests/test_base_import.py b/addons/base_import/tests/test_base_import.py
index 0502af6d0ab..a0031c192e9 100644
--- a/addons/base_import/tests/test_base_import.py
+++ b/addons/base_import/tests/test_base_import.py
@@ -152,7 +152,7 @@ class TestMatchHeadersMultiple(TransactionCase):
 
     def test_noheaders(self):
         self.assertEqual(
-            self.env['base_import.import']._match_headers([], [], {}), (None, None)
+            self.env['base_import.import']._match_headers([], [], {}), ([], {})
         )
 
     def test_nomatch(self):
diff --git a/addons/point_of_sale/static/src/js/db.js b/addons/point_of_sale/static/src/js/db.js
index c2b3fad52f0..ccdd0fb6616 100644
--- a/addons/point_of_sale/static/src/js/db.js
+++ b/addons/point_of_sale/static/src/js/db.js
@@ -477,6 +477,13 @@ var PosDB = core.Class.extend({
         }
         return orders;
     },
+    set_cashier: function(cashier) {
+        // Always update if the user is the same as before
+        this.save('cashier', cashier);
+    },
+    get_cashier: function() {
+        return this.load('cashier');
+    }
 });
 
 return PosDB;
diff --git a/addons/point_of_sale/static/src/js/models.js b/addons/point_of_sale/static/src/js/models.js
index 9b222f12922..4edff2ce8ea 100644
--- a/addons/point_of_sale/static/src/js/models.js
+++ b/addons/point_of_sale/static/src/js/models.js
@@ -240,6 +240,7 @@ exports.PosModel = Backbone.Model.extend({
             }
 
             self.db.set_uuid(self.config.uuid);
+            self.cashier = self.get_cashier();
 
             var orders = self.db.get_orders();
             for (var i = 0; i < orders.length; i++) {
@@ -572,11 +573,12 @@ exports.PosModel = Backbone.Model.extend({
 
     // returns the user who is currently the cashier for this point of sale
     get_cashier: function(){
-        return this.cashier || this.user;
+        return this.db.get_cashier() || this.cashier || this.user;
     },
     // changes the current cashier
     set_cashier: function(user){
         this.cashier = user;
+        this.db.set_cashier(this.cashier);
     },
     //creates a new empty order and sets it as the current order
     add_new_order: function(){
diff --git a/doc/setup/deploy.rst b/doc/setup/deploy.rst
index ec1a31e0a3c..eb5d4cec144 100644
--- a/doc/setup/deploy.rst
+++ b/doc/setup/deploy.rst
@@ -213,6 +213,10 @@ Instead you must have a proxy redirecting requests whose URL starts with
 ``/longpolling/`` to the longpolling port. Other request should be proxied to
 the :option:`normal HTTP port <odoo-bin --xmlrpc-port>`
 
+.. warning:: The livechat worker requires the ``psycogreen`` Python module,
+             which is not always included with all installation packages.
+             It can be manually installed with ``pip install psycogreen``.
+
 Configuration sample
 --------------------
 
diff --git a/odoo/addons/base/base.sql b/odoo/addons/base/base.sql
index 3e3a765a280..56934e13032 100644
--- a/odoo/addons/base/base.sql
+++ b/odoo/addons/base/base.sql
@@ -94,7 +94,7 @@ CREATE TABLE ir_module_module (
     website character varying(256),
     summary character varying(256),
     name character varying(128) NOT NULL,
-    author character varying(128),
+    author character varying,
     icon varchar,
     state character varying(16),
     latest_version character varying(64),