diff --git a/oslo_config/cfg.py b/oslo_config/cfg.py
index bc572003..9fc13d8a 100644
--- a/oslo_config/cfg.py
+++ b/oslo_config/cfg.py
@@ -409,6 +409,7 @@ import os
 import string
 import sys
 
+import debtcollector
 from debtcollector import removals
 import six
 from six import moves
@@ -2479,11 +2480,8 @@ class ConfigOpts(collections.Mapping):
         :raises: NoSuchOptError, NoSuchGroupError
         """
         opt_info = self._get_opt_info(name, group)
-        if enforce_type and override is not None:
-            opt_info['override'] = self._convert_value(override,
-                                                       opt_info['opt'])
-        else:
-            opt_info['override'] = override
+        opt_info['override'] = self._get_enforced_type_value(
+            opt_info['opt'], override, enforce_type)
 
     @__clear_cache
     def set_default(self, name, default, group=None, enforce_type=False):
@@ -2501,11 +2499,28 @@ class ConfigOpts(collections.Mapping):
         :raises: NoSuchOptError, NoSuchGroupError
         """
         opt_info = self._get_opt_info(name, group)
-        if enforce_type and default is not None:
-            opt_info['default'] = self._convert_value(default,
-                                                      opt_info['opt'])
+        opt_info['default'] = self._get_enforced_type_value(
+            opt_info['opt'], default, enforce_type)
+
+    def _get_enforced_type_value(self, opt, value, enforce_type):
+        if value is None:
+            return None
+        try:
+            converted = self._convert_value(value, opt)
+        except (ValueError, TypeError):
+            if enforce_type:
+                raise
+            debtcollector.deprecate(
+                "The argument enforce_type is changing its "
+                "default value to True and then will be removed completely, "
+                "please fix the invalid %s value '%s' for option '%s'."
+                % (repr(opt.type), value, opt.name),
+                version=4.0
+            )
+        if enforce_type:
+            return converted
         else:
-            opt_info['default'] = default
+            return value
 
     @__clear_cache
     def clear_override(self, name, group=None):
diff --git a/oslo_config/tests/test_cfg.py b/oslo_config/tests/test_cfg.py
index 188d69e0..4c2f48bf 100644
--- a/oslo_config/tests/test_cfg.py
+++ b/oslo_config/tests/test_cfg.py
@@ -2993,6 +2993,21 @@ class OverridesTestCase(BaseTestCase):
         self.conf.clear_default('foo')
         self.assertEqual('foo', self.conf.foo)
 
+    @mock.patch('debtcollector.deprecate')
+    def test_deprecation_wrong_type_default(self, deprecate):
+        self.conf.register_opt(cfg.IntOpt('foo', default=1))
+        self.conf([])
+        self.assertEqual(1, self.conf.foo)
+        self.conf.set_default('foo', "not_really_a_int")
+        self.assertEqual('not_really_a_int', self.conf.foo)
+        self.conf.clear_default('foo')
+        self.assertEqual(1, self.conf.foo)
+        deprecate.assert_called_once_with(
+            "The argument enforce_type is changing its default value to True "
+            "and then will be removed completely, please fix the invalid "
+            "Integer value 'not_really_a_int' for option 'foo'.",
+            version=4.0)
+
     def test_override(self):
         self.conf.register_opt(cfg.StrOpt('foo'))
         self.conf.set_override('foo', 'bar')
@@ -3070,6 +3085,20 @@ class OverridesTestCase(BaseTestCase):
         self.conf.clear_override('foo')
         self.assertIsNone(self.conf.foo)
 
+    @mock.patch('debtcollector.deprecate')
+    def test_deprecation_wrong_type_override(self, deprecate):
+        self.conf.register_opt(cfg.IntOpt('foo'))
+        self.conf.set_override('foo', "not_really_a_int")
+        self.conf([])
+        self.assertEqual('not_really_a_int', self.conf.foo)
+        self.conf.clear_override('foo')
+        self.assertIsNone(self.conf.foo)
+        deprecate.assert_called_once_with(
+            "The argument enforce_type is changing its default value to True "
+            "and then will be removed completely, please fix the invalid "
+            "Integer value 'not_really_a_int' for option 'foo'.",
+            version=4.0)
+
     def test_set_override_in_choices(self):
         self.conf.register_group(cfg.OptGroup('f'))
         self.conf.register_cli_opt(cfg.StrOpt('oo', choices=('a', 'b')),