diff --git a/addons/auth_signup/models/__init__.py b/addons/auth_signup/models/__init__.py
index 44dc1ee6b11..a25160266e7 100644
--- a/addons/auth_signup/models/__init__.py
+++ b/addons/auth_signup/models/__init__.py
@@ -4,3 +4,4 @@ from . import res_config_settings
 from . import ir_http
 from . import res_partner
 from . import res_users
+from . import ir_model_fields
diff --git a/addons/auth_signup/models/ir_model_fields.py b/addons/auth_signup/models/ir_model_fields.py
new file mode 100644
index 00000000000..828b9de8346
--- /dev/null
+++ b/addons/auth_signup/models/ir_model_fields.py
@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details
+
+from odoo import models
+
+
+# This is a nasty hack, targeted for V11 only
+class IrModelFields(models.Model):
+    _inherit = 'ir.model.fields'
+
+    def unlink(self):
+        # Prevent the deletion of some `shared` fields... -_-
+        self = self.filtered(
+            lambda rec: not (
+                rec.model == 'res.config.settings'
+                and rec.name == 'auth_signup_uninvited'
+            )
+        )
+        return super(IrModelFields, self).unlink()
diff --git a/addons/sale/models/__init__.py b/addons/sale/models/__init__.py
index 5f6e7ba2857..7a157566790 100644
--- a/addons/sale/models/__init__.py
+++ b/addons/sale/models/__init__.py
@@ -12,3 +12,4 @@ from . import sale
 from . import res_config_settings
 from . import sale_layout
 from . import sales_team
+from . import ir_model_fields
diff --git a/addons/sale/models/ir_model_fields.py b/addons/sale/models/ir_model_fields.py
new file mode 100644
index 00000000000..828b9de8346
--- /dev/null
+++ b/addons/sale/models/ir_model_fields.py
@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details
+
+from odoo import models
+
+
+# This is a nasty hack, targeted for V11 only
+class IrModelFields(models.Model):
+    _inherit = 'ir.model.fields'
+
+    def unlink(self):
+        # Prevent the deletion of some `shared` fields... -_-
+        self = self.filtered(
+            lambda rec: not (
+                rec.model == 'res.config.settings'
+                and rec.name == 'auth_signup_uninvited'
+            )
+        )
+        return super(IrModelFields, self).unlink()
diff --git a/addons/website/models/ir_model_fields.py b/addons/website/models/ir_model_fields.py
index 1e963bf650e..51f5c2a7dc5 100644
--- a/addons/website/models/ir_model_fields.py
+++ b/addons/website/models/ir_model_fields.py
@@ -1,17 +1,15 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details
 
-from odoo import api, models
+from odoo import models
 
 
 # This is a nasty hack, targeted for V11 only
 class IrModelFields(models.Model):
     _inherit = 'ir.model.fields'
 
-    @api.multi
     def unlink(self):
-        # Prevent the deletion of social_* fields defined in res.company if
-        # the other module is installed
+        # Prevent the deletion of some `shared` fields... -_-
         social = (
             'social_facebook',
             'social_github',
@@ -23,8 +21,9 @@ class IrModelFields(models.Model):
 
         self = self.filtered(
             lambda rec: not (
-                rec.model == 'res.company' and
-                rec.name in social
+                (rec.model == 'res.company' and rec.name in social)
+                or (rec.model == 'res.config.settings'
+                    and rec.name == 'auth_signup_uninvited')
             )
         )
         return super(IrModelFields, self).unlink()