diff --git a/addons/crm/models/crm_lead.py b/addons/crm/models/crm_lead.py
index e95a3bfa1ed..0d64ebf943c 100644
--- a/addons/crm/models/crm_lead.py
+++ b/addons/crm/models/crm_lead.py
@@ -1902,7 +1902,7 @@ class Lead(models.Model):
             'is_company': is_company,
             'type': 'contact'
         }
-        if self.lang_id:
+        if self.lang_id.active:
             res['lang'] = self.lang_id.code
         return res
 
diff --git a/addons/crm/tests/test_crm_lead_convert.py b/addons/crm/tests/test_crm_lead_convert.py
index 1fd7ccdaf4b..f329e557c58 100644
--- a/addons/crm/tests/test_crm_lead_convert.py
+++ b/addons/crm/tests/test_crm_lead_convert.py
@@ -246,6 +246,27 @@ class TestLeadConvert(crm_common.TestLeadConvertCommon):
         # TDE FIXME: should take into account normalized email version, not encoded one
         # self.assertEqual(convert.partner_id, customer)
 
+    @users('user_sales_manager')
+    def test_lead_convert_no_lang(self):
+        """ Ensure converting a lead with an archived language correctly falls back on the default partner language. """
+        inactive_lang = self.env["res.lang"].sudo().create({
+            'code': 'en_ZZ',
+            'name': 'Inactive Lang',
+            'active': False,
+        })
+
+        lead = self.lead_1.with_user(self.env.user)
+        lead.lang_id = inactive_lang
+
+        convert = self.env['crm.lead2opportunity.partner'].with_context({
+            'active_model': 'crm.lead',
+            'active_id': self.lead_1.id,
+            'active_ids': self.lead_1.ids,
+        }).create({'action': 'create'})
+        convert.action_apply()
+        self.assertTrue(lead.partner_id)
+        self.assertEqual(lead.partner_id.lang, 'en_US')
+
     @users('user_sales_manager')
     def test_lead_convert_internals(self):
         """ Test internals of convert wizard """
diff --git a/addons/crm/tests/test_crm_lead_notification.py b/addons/crm/tests/test_crm_lead_notification.py
index 1ecc805ad86..c31397b60f9 100644
--- a/addons/crm/tests/test_crm_lead_notification.py
+++ b/addons/crm/tests/test_crm_lead_notification.py
@@ -112,7 +112,7 @@ class NewLeadNotification(TestCrmCommon):
             }
         ])
         expected_list = [
-            (False, self.test_email, None, 'Customer Email', {'lang': 'fr_FR'}),
+            (False, self.test_email, None, 'Customer Email', {'lang': None}),
             (False, self.test_email, 'en_US', 'Customer Email', {'lang': 'en_US'}),
         ]
         for lead, expected in zip(leads, expected_list):
@@ -121,7 +121,7 @@ class NewLeadNotification(TestCrmCommon):
                 self.assertEqual(len(res), 1)
                 self.assertEqual(res[0][:4], expected[:4])
                 for partner_fname in expected[4]:
-                    found = res[0][4][partner_fname]
+                    found = res[0][4].get(partner_fname)
                     expected = expected[4][partner_fname]
                     self.assertEqual(
                         found, expected,