diff --git a/addons/account/models/company.py b/addons/account/models/company.py
index 5ea0db1cd95..ea47862f89e 100644
--- a/addons/account/models/company.py
+++ b/addons/account/models/company.py
@@ -12,6 +12,22 @@ from odoo.tools.float_utils import float_round, float_is_zero
 from odoo.tools import date_utils
 
 
+MONTH_SELECTION = [
+    ('1', 'January'),
+    ('2', 'February'),
+    ('3', 'March'),
+    ('4', 'April'),
+    ('5', 'May'),
+    ('6', 'June'),
+    ('7', 'July'),
+    ('8', 'August'),
+    ('9', 'September'),
+    ('10', 'October'),
+    ('11', 'November'),
+    ('12', 'December'),
+]
+
+
 class ResCompany(models.Model):
     _inherit = "res.company"
 
@@ -20,7 +36,7 @@ class ResCompany(models.Model):
 
     #TODO check all the options/fields are in the views (settings + company form view)
     fiscalyear_last_day = fields.Integer(default=31, required=True)
-    fiscalyear_last_month = fields.Selection([(1, 'January'), (2, 'February'), (3, 'March'), (4, 'April'), (5, 'May'), (6, 'June'), (7, 'July'), (8, 'August'), (9, 'September'), (10, 'October'), (11, 'November'), (12, 'December')], default=12, required=True)
+    fiscalyear_last_month = fields.Selection(MONTH_SELECTION, default='12', required=True)
     period_lock_date = fields.Date(string="Lock Date for Non-Advisers", help="Only users with the 'Adviser' role can edit accounts prior to and inclusive of this date. Use it for period locking inside an open fiscal year, for example.")
     fiscalyear_lock_date = fields.Date(string="Lock Date", help="No users, including Advisers, can edit accounts prior to and inclusive of this date. Use it for fiscal year locking for example.")
     transfer_account_id = fields.Many2one('account.account',
@@ -93,7 +109,7 @@ Best Regards,'''))
     def _check_fiscalyear_last_day(self):
         # if the user explicitly chooses the 29th of February we allow it:
         # there is no "fiscalyear_last_year" so we do not know his intentions.
-        if self.fiscalyear_last_day == 29 and self.fiscalyear_last_month == 2:
+        if self.fiscalyear_last_day == 29 and self.fiscalyear_last_month == '2':
             return
 
         if self.account_opening_date:
@@ -101,7 +117,7 @@ Best Regards,'''))
         else:
             year = datetime.now().year
 
-        max_day = calendar.monthrange(year, self.fiscalyear_last_month)[1]
+        max_day = calendar.monthrange(year, int(self.fiscalyear_last_month))[1]
         if self.fiscalyear_last_day > max_day:
             raise ValidationError(_("Invalid fiscal year last day"))
 
@@ -214,7 +230,7 @@ Best Regards,'''))
             }
 
         date_from, date_to = date_utils.get_fiscal_year(
-            current_date, day=self.fiscalyear_last_day, month=self.fiscalyear_last_month)
+            current_date, day=self.fiscalyear_last_day, month=int(self.fiscalyear_last_month))
 
         date_from_str = date_from.strftime(DEFAULT_SERVER_DATE_FORMAT)
         date_to_str = date_to.strftime(DEFAULT_SERVER_DATE_FORMAT)
@@ -357,7 +373,7 @@ Best Regards,'''))
                 raise UserError(_("Please install a chart of accounts or create a miscellaneous journal before proceeding."))
 
             today = datetime.today().date()
-            opening_date = today.replace(month=self.fiscalyear_last_month, day=self.fiscalyear_last_day) + timedelta(days=1)
+            opening_date = today.replace(month=int(self.fiscalyear_last_month), day=self.fiscalyear_last_day) + timedelta(days=1)
             if opening_date > today:
                 opening_date = opening_date + relativedelta(years=-1)
 
diff --git a/addons/account/tests/test_account_fiscal_year.py b/addons/account/tests/test_account_fiscal_year.py
index 7fe5e6a966e..0bbf73249aa 100644
--- a/addons/account/tests/test_account_fiscal_year.py
+++ b/addons/account/tests/test_account_fiscal_year.py
@@ -28,7 +28,7 @@ class TestFiscalPosition(AccountingTestCase):
         '''Basic case with a fiscal year xxxx-01-01 - xxxx-12-31.'''
         company = self.env.ref('base.main_company')
         company.fiscalyear_last_day = 31
-        company.fiscalyear_last_month = 12
+        company.fiscalyear_last_month = '12'
 
         self.check_compute_fiscal_year(
             company,
@@ -48,7 +48,7 @@ class TestFiscalPosition(AccountingTestCase):
         '''Case with a leap year ending the 29 February.'''
         company = self.env.ref('base.main_company')
         company.fiscalyear_last_day = 29
-        company.fiscalyear_last_month = 2
+        company.fiscalyear_last_month = '2'
 
         self.check_compute_fiscal_year(
             company,
@@ -68,7 +68,7 @@ class TestFiscalPosition(AccountingTestCase):
         '''Case with a leap year ending the 28 February.'''
         company = self.env.ref('base.main_company')
         company.fiscalyear_last_day = 28
-        company.fiscalyear_last_month = 2
+        company.fiscalyear_last_month = '2'
 
         self.check_compute_fiscal_year(
             company,
@@ -88,7 +88,7 @@ class TestFiscalPosition(AccountingTestCase):
         '''Case with custom fiscal years.'''
         company = self.env.ref('base.main_company')
         company.fiscalyear_last_day = 31
-        company.fiscalyear_last_month = 12
+        company.fiscalyear_last_month = '12'
 
         # Create custom fiscal year covering the 6 first months of 2017.
         self.env['account.fiscal.year'].create({
diff --git a/addons/account/wizard/setup_wizards.py b/addons/account/wizard/setup_wizards.py
index 2aac7495fd5..cde10af75f1 100644
--- a/addons/account/wizard/setup_wizards.py
+++ b/addons/account/wizard/setup_wizards.py
@@ -16,8 +16,7 @@ class FinancialYearOpeningWizard(models.TransientModel):
     opening_date = fields.Date(string='Opening Date', required=True, related='company_id.account_opening_date', help="Date from which the accounting is managed in Odoo. It is the date of the opening entry.", readonly=False)
     fiscalyear_last_day = fields.Integer(related="company_id.fiscalyear_last_day", required=True, readonly=False,
                                          help="Fiscal year last day.")
-    fiscalyear_last_month = fields.Selection(selection=[(1, 'January'), (2, 'February'), (3, 'March'), (4, 'April'), (5, 'May'), (6, 'June'), (7, 'July'), (8, 'August'), (9, 'September'), (10, 'October'), (11, 'November'), (12, 'December')],
-                                             related="company_id.fiscalyear_last_month", readonly=False,
+    fiscalyear_last_month = fields.Selection(related="company_id.fiscalyear_last_month", readonly=False,
                                              required=True,
                                              help="Fiscal year last month.")
 
@@ -33,7 +32,7 @@ class FinancialYearOpeningWizard(models.TransientModel):
         # fields is done one field at a time.
         for wiz in self:
             try:
-                date(2020, wiz.fiscalyear_last_month, wiz.fiscalyear_last_day)
+                date(2020, int(wiz.fiscalyear_last_month), wiz.fiscalyear_last_day)
             except ValueError:
                 raise ValidationError(
                     _('Incorrect fiscal year date: day is out of range for month. Month: %s; Day: %s') %
diff --git a/addons/stock/models/res_config_settings.py b/addons/stock/models/res_config_settings.py
index ebf7d339d39..3eca680cce7 100644
--- a/addons/stock/models/res_config_settings.py
+++ b/addons/stock/models/res_config_settings.py
@@ -8,9 +8,9 @@ class ResConfigSettings(models.TransientModel):
     _inherit = 'res.config.settings'
 
     module_procurement_jit = fields.Selection([
-        (1, 'Immediately after sales order confirmation'),
-        (0, 'Manually or based on automatic scheduler')
-        ], "Reservation",
+        ('1', 'Immediately after sales order confirmation'),
+        ('0', 'Manually or based on automatic scheduler')
+        ], "Reservation", default='0',
         help="Reserving products manually in delivery orders or by running the scheduler is advised to better manage priorities in case of long customer lead times or/and frequent stock-outs.")
     module_product_expiry = fields.Boolean("Expiration Dates",
         help="Track following dates on lots & serial numbers: best before, removal, end of life, alert. \n Such dates are set automatically at lot/serial number creation based on values set on the product (in days).")
diff --git a/addons/stock/wizard/stock_quantity_history.py b/addons/stock/wizard/stock_quantity_history.py
index 595a5c8de88..e925073bc0c 100644
--- a/addons/stock/wizard/stock_quantity_history.py
+++ b/addons/stock/wizard/stock_quantity_history.py
@@ -9,15 +9,15 @@ class StockQuantityHistory(models.TransientModel):
     _description = 'Stock Quantity History'
 
     compute_at_date = fields.Selection([
-        (0, 'Current Inventory'),
-        (1, 'At a Specific Date')
-    ], string="Compute", help="Choose to analyze the current inventory or from a specific date in the past.")
+        ('0', 'Current Inventory'),
+        ('1', 'At a Specific Date')
+    ], default='0', string="Compute", help="Choose to analyze the current inventory or from a specific date in the past.")
     date = fields.Datetime('Inventory at Date', help="Choose a date to get the inventory at that date", default=fields.Datetime.now)
 
     def open_table(self):
         self.ensure_one()
 
-        if self.compute_at_date:
+        if int(self.compute_at_date):
             tree_view_id = self.env.ref('stock.view_stock_product_tree').id
             form_view_id = self.env.ref('stock.product_form_view_procurement_button').id
             # We pass `to_date` in the context so that `qty_available` will be computed across
diff --git a/addons/stock/wizard/stock_quantity_history.xml b/addons/stock/wizard/stock_quantity_history.xml
index c464bf7b42d..bc18695e5c6 100644
--- a/addons/stock/wizard/stock_quantity_history.xml
+++ b/addons/stock/wizard/stock_quantity_history.xml
@@ -8,7 +8,7 @@
                 <group>
                     <group>
                         <field name="compute_at_date" widget="radio"/>
-                        <field name="date" attrs="{'invisible': [('compute_at_date', '=', 0)]}"/>
+                        <field name="date" attrs="{'invisible': [('compute_at_date', '=', '0')]}"/>
                     </group>
                 </group>
                 <footer>
@@ -25,7 +25,7 @@
         <field name="view_mode">form</field>
         <field name="view_id" ref="view_stock_quantity_history"/>
         <field name="target">new</field>
-        <field name="context">{'default_compute_at_date': 0}</field>
+        <field name="context">{'default_compute_at_date': '0'}</field>
     </record>
     <menuitem id="menu_valuation" name="Inventory Report" parent="stock.menu_warehouse_report" sequence="100" action="action_stock_quantity_history"/>
 </odoo>
diff --git a/addons/stock_account/views/stock_account_views.xml b/addons/stock_account/views/stock_account_views.xml
index a9dbf024f2e..45abf2db497 100644
--- a/addons/stock_account/views/stock_account_views.xml
+++ b/addons/stock_account/views/stock_account_views.xml
@@ -58,7 +58,7 @@
                     <group>
                         <group>
                             <field name="compute_at_date" widget="radio"/>
-                            <field name="date" attrs="{'invisible': [('compute_at_date', '=', 0)]}"/>
+                            <field name="date" attrs="{'invisible': [('compute_at_date', '=', '0')]}"/>
                         </group>
                     </group>
                     <footer>
@@ -105,7 +105,7 @@
             <field name="view_mode">form</field>
             <field name="view_id" ref="stock_account.view_stock_quantity_history"/>
             <field name="target">new</field>
-            <field name="context">{'default_compute_at_date': 0, 'valuation': True}</field>
+            <field name="context">{'default_compute_at_date': '0', 'valuation': True}</field>
         </record>
         <menuitem id="menu_valuation" name="Inventory Valuation" parent="stock.menu_warehouse_report" sequence="110" action="action_stock_inventory_valuation"/>
 
diff --git a/addons/stock_account/wizard/stock_quantity_history.py b/addons/stock_account/wizard/stock_quantity_history.py
index b8e010b04e5..59e5ab01c58 100644
--- a/addons/stock_account/wizard/stock_quantity_history.py
+++ b/addons/stock_account/wizard/stock_quantity_history.py
@@ -12,7 +12,7 @@ class StockQuantityHistory(models.TransientModel):
 
         self.env['stock.move']._run_fifo_vacuum()
 
-        if self.compute_at_date:
+        if int(self.compute_at_date):
             tree_view_id = self.env.ref('stock_account.view_stock_product_tree2').id
             form_view_id = self.env.ref('stock.product_form_view_procurement_button').id
             search_view_id = self.env.ref('stock_account.view_inventory_valuation_search').id
diff --git a/addons/web/controllers/main.py b/addons/web/controllers/main.py
index 57c86a2c6d6..853d008c802 100644
--- a/addons/web/controllers/main.py
+++ b/addons/web/controllers/main.py
@@ -599,6 +599,7 @@ class WebClient(http.Controller):
             lang_params = langs.read([
                 "name", "direction", "date_format", "time_format",
                 "grouping", "decimal_point", "thousands_sep", "week_start"])[0]
+            lang_params['week_start'] = int(lang_params['week_start'])
 
         # Regional languages (ll_CC) must inherit/override their parent lang (ll), but this is
         # done server-side when the language is loaded, so we only need to load the user's lang.
diff --git a/addons/web_editor/models/test_models.py b/addons/web_editor/models/test_models.py
index d5ef48dc2af..282b703c03d 100644
--- a/addons/web_editor/models/test_models.py
+++ b/addons/web_editor/models/test_models.py
@@ -19,12 +19,6 @@ class ConverterTest(models.Model):
     binary = fields.Binary(attachment=False)
     date = fields.Date()
     datetime = fields.Datetime()
-    selection = fields.Selection([
-        (1, "réponse A"),
-        (2, "réponse B"),
-        (3, "réponse C"),
-        (4, "réponse <D>"),
-    ])
     selection_str = fields.Selection([
         ('A', "Qu'il n'est pas arrivé à Toronto"),
         ('B', "Qu'il était supposé arriver à Toronto"),
diff --git a/addons/web_editor/tests/test_converter.py b/addons/web_editor/tests/test_converter.py
index bb778b07799..cfa62e52ac2 100644
--- a/addons/web_editor/tests/test_converter.py
+++ b/addons/web_editor/tests/test_converter.py
@@ -158,9 +158,6 @@ class TestConvertBack(common.TransactionCase):
         self.field_roundtrip('char', "foo bar")
         self.field_roundtrip('char', "ⒸⓄⓇⒼⒺ")
 
-    def test_selection(self):
-        self.field_roundtrip('selection', 3)
-
     def test_selection_str(self):
         self.field_roundtrip('selection_str', 'B')
 
diff --git a/odoo/addons/base/models/res_config.py b/odoo/addons/base/models/res_config.py
index 32beb3b5742..ac2b9a153ae 100644
--- a/odoo/addons/base/models/res_config.py
+++ b/odoo/addons/base/models/res_config.py
@@ -355,7 +355,7 @@ class ResConfigSettings(models.TransientModel, ResConfigModuleInstallationMixin)
             By default 'group' is the group Employee.  Groups are given by their xml id.
             The attribute 'group' may contain several xml ids, separated by commas.
 
-        *   For a selection field like 'group_XXX' composed of 2 integers values ('0' and '1'),
+        *   For a selection field like 'group_XXX' composed of 2 string values ('0' and '1'),
             ``execute`` adds/removes 'implied_group' to/from the implied groups of 'group', 
             depending on the field's value.
             By default 'group' is the group Employee.  Groups are given by their xml id.
@@ -364,9 +364,9 @@ class ResConfigSettings(models.TransientModel, ResConfigModuleInstallationMixin)
         *   For a boolean field like 'module_XXX', ``execute`` triggers the immediate
             installation of the module named 'XXX' if the field has value ``True``.
 
-        *   For a selection field like 'module_XXX' composed of 2 integers values ('0' and '1'), 
+        *   For a selection field like 'module_XXX' composed of 2 string values ('0' and '1'), 
             ``execute`` triggers the immediate installation of the module named 'XXX' 
-            if the field has the integer value ``1``.
+            if the field has the value ``'1'``.
 
         *   For a field with no specific prefix BUT an attribute 'config_parameter',
             ``execute``` will save its value in an ir.config.parameter (global setting for the
@@ -419,7 +419,7 @@ class ResConfigSettings(models.TransientModel, ResConfigModuleInstallationMixin)
             [('name', '=', module_name.replace("module_", '')),
             ('state', 'in', ['to install', 'installed', 'to upgrade'])])
 
-        if modules and not field_value:
+        if modules and not int(field_value):
             deps = modules.sudo().downstream_dependencies()
             dep_names = (deps | modules).mapped('shortdesc')
             message = '\n'.join(dep_names)
@@ -508,13 +508,13 @@ class ResConfigSettings(models.TransientModel, ResConfigModuleInstallationMixin)
         for name, groups, implied_group in classified['group']:
             res[name] = all(implied_group in group.implied_ids for group in groups)
             if self._fields[name].type == 'selection':
-                res[name] = int(res[name])
+                res[name] = str(int(res[name]))     # True, False -> '1', '0'
 
         # modules: which modules are installed/to install
         for name, module in classified['module']:
             res[name] = module.state in ('installed', 'to install', 'to upgrade')
             if self._fields[name].type == 'selection':
-                res[name] = int(res[name])
+                res[name] = str(int(res[name]))     # True, False -> '1', '0'
 
         # config: get & convert stored ir.config_parameter (or default)
         WARNING_MESSAGE = "Error when converting value %r of field %s for ir.config.parameter %r"
@@ -580,7 +580,7 @@ class ResConfigSettings(models.TransientModel, ResConfigModuleInstallationMixin)
             for name, groups, implied_group in classified['group']:
                 if self[name] == current_settings[name]:
                     continue
-                if self[name]:
+                if int(self[name]):
                     groups.write({'implied_ids': [(4, implied_group.id)]})
                 else:
                     groups.write({'implied_ids': [(3, implied_group.id)]})
@@ -625,7 +625,7 @@ class ResConfigSettings(models.TransientModel, ResConfigModuleInstallationMixin)
         to_uninstall_modules = self.env['ir.module.module']
         lm = len('module_')
         for name, module in classified['module']:
-            if self[name]:
+            if int(self[name]):
                 to_install.append((name[lm:], module))
             else:
                 if module and module.state in ('installed', 'to upgrade'):
diff --git a/odoo/addons/base/models/res_lang.py b/odoo/addons/base/models/res_lang.py
index 56fea211a11..534c8cb248c 100644
--- a/odoo/addons/base/models/res_lang.py
+++ b/odoo/addons/base/models/res_lang.py
@@ -33,13 +33,13 @@ class Lang(models.Model):
     direction = fields.Selection([('ltr', 'Left-to-Right'), ('rtl', 'Right-to-Left')], required=True, default='ltr')
     date_format = fields.Char(string='Date Format', required=True, default=DEFAULT_DATE_FORMAT)
     time_format = fields.Char(string='Time Format', required=True, default=DEFAULT_TIME_FORMAT)
-    week_start = fields.Selection([(1, 'Monday'),
-                                   (2, 'Tuesday'),
-                                   (3, 'Wednesday'),
-                                   (4, 'Thursday'),
-                                   (5, 'Friday'),
-                                   (6, 'Saturday'),
-                                   (7, 'Sunday')], string='First Day of Week', required=True, default=7)
+    week_start = fields.Selection([('1', 'Monday'),
+                                   ('2', 'Tuesday'),
+                                   ('3', 'Wednesday'),
+                                   ('4', 'Thursday'),
+                                   ('5', 'Friday'),
+                                   ('6', 'Saturday'),
+                                   ('7', 'Sunday')], string='First Day of Week', required=True, default='7')
     grouping = fields.Char(string='Separator Format', required=True, default='[]',
         help="The Separator Format should be like [,n] where 0 < n :starting from Unit digit. "
              "-1 will end the separation. e.g. [3,2,-1] will represent 106500 to be 1,06,500; "
diff --git a/odoo/addons/base/wizard/base_import_language.py b/odoo/addons/base/wizard/base_import_language.py
index 1017806119e..e39c36e89ae 100644
--- a/odoo/addons/base/wizard/base_import_language.py
+++ b/odoo/addons/base/wizard/base_import_language.py
@@ -41,5 +41,9 @@ class BaseLanguageImport(models.TransientModel):
                                       lang_name=this.name, context=this._context)
             except Exception as e:
                 _logger.exception('File unsuccessfully imported, due to format mismatch.')
-                raise UserError(_('File not imported due to format mismatch or a malformed file. (Valid formats are .csv, .po, .pot)\n\nTechnical Details:\n%s') % tools.ustr(e))
+                raise UserError(
+                    _('File %r not imported due to format mismatch or a malformed file.'
+                      ' (Valid formats are .csv, .po, .pot)\n\nTechnical Details:\n%s') % \
+                    (this.filename, tools.ustr(e))
+                )
         return True
diff --git a/odoo/addons/test_converter/models.py b/odoo/addons/test_converter/models.py
index 29a8bcefebf..1cb39b9cd47 100644
--- a/odoo/addons/test_converter/models.py
+++ b/odoo/addons/test_converter/models.py
@@ -15,12 +15,6 @@ class test_model(models.Model):
     binary = fields.Binary(attachment=False)
     date = fields.Date()
     datetime = fields.Datetime()
-    selection = fields.Selection([
-        (1, "réponse A"),
-        (2, "réponse B"),
-        (3, "réponse C"),
-        (4, "réponse <D>"),
-    ])
     selection_str = fields.Selection([
         ('A', u"Qu'il n'est pas arrivé à Toronto"),
         ('B', u"Qu'il était supposé arriver à Toronto"),
diff --git a/odoo/addons/test_converter/tests/test_html.py b/odoo/addons/test_converter/tests/test_html.py
index bc157ab84e4..cf3f4c198ec 100644
--- a/odoo/addons/test_converter/tests/test_html.py
+++ b/odoo/addons/test_converter/tests/test_html.py
@@ -234,10 +234,6 @@ class TestBinaryExport(TestBasicExport):
 
 class TestSelectionExport(TestBasicExport):
     def test_selection(self):
-        converter = self.get_converter('selection')
-        value = converter(4)
-        self.assertEqual(value, e(u"réponse <D>"))
-
         converter = self.get_converter('selection_str')
         value = converter('C')
         self.assertEqual(value, u"Qu'est-ce qu'il fout ce maudit pancake, tabernacle ?")
diff --git a/odoo/addons/test_impex/models.py b/odoo/addons/test_impex/models.py
index 45cf4af4402..726bf9041c0 100644
--- a/odoo/addons/test_impex/models.py
+++ b/odoo/addons/test_impex/models.py
@@ -25,7 +25,7 @@ MODELS = [
     ('date', fields.Date()),
     ('datetime', fields.Datetime()),
     ('text', fields.Text()),
-    ('selection', fields.Selection([(1, "Foo"), (2, "Bar"), (3, "Qux"), (4, '')])),
+    ('selection', fields.Selection([('1', "Foo"), ('2', "Bar"), ('3', "Qux"), ('4', '')])),
     ('selection.function', fields.Selection(selection_fn)),
     # just relate to an integer
     ('many2one', fields.Many2one('export.integer')),
@@ -143,7 +143,7 @@ class SelectionWithDefault(models.Model):
     _description = 'Export Selection With Default'
 
     const = fields.Integer(default=4)
-    value = fields.Selection([(1, "Foo"), (2, "Bar")], default=2)
+    value = fields.Selection([('1', "Foo"), ('2', "Bar")], default='2')
 
 
 class RecO2M(models.Model):
diff --git a/odoo/addons/test_impex/tests/test_export.py b/odoo/addons/test_impex/tests/test_export.py
index 264db66e992..3fc071e7454 100644
--- a/odoo/addons/test_impex/tests/test_export.py
+++ b/odoo/addons/test_impex/tests/test_export.py
@@ -276,7 +276,7 @@ class test_selection(CreatorCase):
         """ selections export the *label* for their value
         """
         self.assertEqual(
-            self.export(2),
+            self.export('2'),
             [[u"Bar"]])
 
     def test_localized_export(self):
@@ -291,7 +291,7 @@ class test_selection(CreatorCase):
                 'value': value
             })
         self.assertEqual(
-            self.export(2, context={'lang': 'fr_FR'}),
+            self.export('2', context={'lang': 'fr_FR'}),
             [[u'titi']])
 
 
diff --git a/odoo/addons/test_impex/tests/test_load.py b/odoo/addons/test_impex/tests/test_load.py
index 34d6aa97de0..2d28d11231a 100644
--- a/odoo/addons/test_impex/tests/test_load.py
+++ b/odoo/addons/test_impex/tests/test_load.py
@@ -438,7 +438,7 @@ class test_selection(ImporterCase):
         ])
         self.assertEqual(len(result['ids']), 4)
         self.assertFalse(result['messages'])
-        self.assertEqual([3, 2, 1, 2], values(self.read()))
+        self.assertEqual(['3', '2', '1', '2'], values(self.read()))
 
     def test_imported_translated(self):
         self.add_translations(
@@ -452,7 +452,7 @@ class test_selection(ImporterCase):
         self.assertEqual(len(result['ids']), 3)
         self.assertFalse(result['messages'])
 
-        self.assertEqual([3, 1, 2], values(self.read()))
+        self.assertEqual(['3', '1', '2'], values(self.read()))
 
         result = self.import_(['value'], [['Foo']], context={'lang': 'fr_FR'})
         self.assertEqual(len(result['ids']), 1)
@@ -465,7 +465,7 @@ class test_selection(ImporterCase):
             u"Value 'Baz' not found in selection field 'Value'",
             moreinfo="Foo Bar Qux 4".split())])
 
-        result = self.import_(['value'], [[42]])
+        result = self.import_(['value'], [['42']])
         self.assertIs(result['ids'], False)
         self.assertEqual(result['messages'], [message(
             u"Value '42' not found in selection field 'Value'",
@@ -495,7 +495,7 @@ class test_selection_with_default(ImporterCase):
 
         self.assertEqual(
             values(self.read()),
-            [2])
+            ['2'])
 
 
 class test_selection_function(ImporterCase):
diff --git a/odoo/fields.py b/odoo/fields.py
index 6d462a1713d..5d1701447a4 100644
--- a/odoo/fields.py
+++ b/odoo/fields.py
@@ -1859,6 +1859,7 @@ class Selection(Field):
     <field-incremental-definition>`.
     """
     type = 'selection'
+    column_type = ('varchar', pg_varchar())
     _slots = {
         'selection': None,              # [(value, string), ...], function or method name
         'validate': True,               # whether validating upon write
@@ -1867,18 +1868,12 @@ class Selection(Field):
     def __init__(self, selection=Default, string=Default, **kwargs):
         super(Selection, self).__init__(selection=selection, string=string, **kwargs)
 
-    @property
-    def column_type(self):
-        if (self.selection and
-                isinstance(self.selection, list) and
-                isinstance(self.selection[0][0], int)):
-            return ('int4', 'integer')
-        else:
-            return ('varchar', pg_varchar())
-
     def _setup_regular_base(self, model):
         super(Selection, self)._setup_regular_base(model)
         assert self.selection is not None, "Field %s without selection" % self
+        if isinstance(self.selection, list):
+            assert all(isinstance(v, str) for v, _ in self.selection), \
+                "Field %s with non-str value in selection" % self
 
     def _setup_related_full(self, model):
         super(Selection, self)._setup_related_full(model)