diff --git a/django/conf/__init__.py b/django/conf/__init__.py
index da461ecc026..e03369d3217 100644
--- a/django/conf/__init__.py
+++ b/django/conf/__init__.py
@@ -222,6 +222,9 @@ class Settings:
                 raise ImproperlyConfigured(
                     "DEFAULT_FILE_STORAGE/STORAGES are mutually exclusive."
                 )
+            self.STORAGES[DEFAULT_STORAGE_ALIAS] = {
+                "BACKEND": self.DEFAULT_FILE_STORAGE
+            }
             warnings.warn(DEFAULT_FILE_STORAGE_DEPRECATED_MSG, RemovedInDjango51Warning)
 
         if self.is_overridden("STATICFILES_STORAGE"):
@@ -229,7 +232,22 @@ class Settings:
                 raise ImproperlyConfigured(
                     "STATICFILES_STORAGE/STORAGES are mutually exclusive."
                 )
+            self.STORAGES[STATICFILES_STORAGE_ALIAS] = {
+                "BACKEND": self.STATICFILES_STORAGE
+            }
             warnings.warn(STATICFILES_STORAGE_DEPRECATED_MSG, RemovedInDjango51Warning)
+        # RemovedInDjango51Warning.
+        if self.is_overridden("STORAGES"):
+            setattr(
+                self,
+                "DEFAULT_FILE_STORAGE",
+                self.STORAGES.get(DEFAULT_STORAGE_ALIAS, {}).get("BACKEND"),
+            )
+            setattr(
+                self,
+                "STATICFILES_STORAGE",
+                self.STORAGES.get(STATICFILES_STORAGE_ALIAS, {}).get("BACKEND"),
+            )
 
     def is_overridden(self, setting):
         return setting in self._explicit_settings
@@ -276,14 +294,28 @@ class UserSettingsHolder:
         super().__setattr__(name, value)
         # RemovedInDjango51Warning.
         if name == "STORAGES":
-            self.STORAGES.setdefault(
-                DEFAULT_STORAGE_ALIAS,
-                {"BACKEND": "django.core.files.storage.FileSystemStorage"},
-            )
-            self.STORAGES.setdefault(
-                STATICFILES_STORAGE_ALIAS,
-                {"BACKEND": "django.contrib.staticfiles.storage.StaticFilesStorage"},
-            )
+            if default_file_storage := self.STORAGES.get(DEFAULT_STORAGE_ALIAS):
+                super().__setattr__(
+                    "DEFAULT_FILE_STORAGE", default_file_storage.get("BACKEND")
+                )
+            else:
+                self.STORAGES.setdefault(
+                    DEFAULT_STORAGE_ALIAS,
+                    {"BACKEND": "django.core.files.storage.FileSystemStorage"},
+                )
+            if staticfiles_storage := self.STORAGES.get(STATICFILES_STORAGE_ALIAS):
+                super().__setattr__(
+                    "STATICFILES_STORAGE", staticfiles_storage.get("BACKEND")
+                )
+            else:
+                self.STORAGES.setdefault(
+                    STATICFILES_STORAGE_ALIAS,
+                    {
+                        "BACKEND": (
+                            "django.contrib.staticfiles.storage.StaticFilesStorage"
+                        ),
+                    },
+                )
 
     def __delattr__(self, name):
         self._deleted.add(name)
diff --git a/docs/releases/4.2.5.txt b/docs/releases/4.2.5.txt
index 23ba728da56..480b21d9028 100644
--- a/docs/releases/4.2.5.txt
+++ b/docs/releases/4.2.5.txt
@@ -12,3 +12,7 @@ Bugfixes
 * Fixed a regression in Django 4.2 that caused an incorrect validation of
   ``CheckConstraints`` on ``__isnull`` lookups against ``JSONField``
   (:ticket:`34754`).
+
+* Fixed a bug in Django 4.2 where the deprecated ``DEFAULT_FILE_STORAGE`` and
+  ``STATICFILES_STORAGE`` settings were not synced with ``STORAGES``
+  (:ticket:`34773`).
diff --git a/tests/deprecation/test_storages.py b/tests/deprecation/test_storages.py
index 71ed3acdb03..0574f3e880f 100644
--- a/tests/deprecation/test_storages.py
+++ b/tests/deprecation/test_storages.py
@@ -39,8 +39,36 @@ class StaticfilesStorageDeprecationTests(TestCase):
         )
         sys.modules["fake_settings_module"] = settings_module
         try:
-            with self.assertRaisesMessage(RemovedInDjango51Warning, self.msg):
-                Settings("fake_settings_module")
+            with self.assertWarnsMessage(RemovedInDjango51Warning, self.msg):
+                fake_settings = Settings("fake_settings_module")
+            self.assertEqual(
+                fake_settings.STORAGES[STATICFILES_STORAGE_ALIAS],
+                {
+                    "BACKEND": (
+                        "django.contrib.staticfiles.storage.ManifestStaticFilesStorage"
+                    ),
+                },
+            )
+        finally:
+            del sys.modules["fake_settings_module"]
+
+    def test_settings_storages_init(self):
+        settings_module = ModuleType("fake_settings_module")
+        settings_module.USE_TZ = True
+        settings_module.STORAGES = {
+            STATICFILES_STORAGE_ALIAS: {
+                "BACKEND": (
+                    "django.contrib.staticfiles.storage.ManifestStaticFilesStorage"
+                )
+            }
+        }
+        sys.modules["fake_settings_module"] = settings_module
+        try:
+            fake_settings = Settings("fake_settings_module")
+            self.assertEqual(
+                fake_settings.STATICFILES_STORAGE,
+                "django.contrib.staticfiles.storage.ManifestStaticFilesStorage",
+            )
         finally:
             del sys.modules["fake_settings_module"]
 
@@ -101,6 +129,26 @@ class StaticfilesStorageDeprecationTests(TestCase):
             )
             self.assertIsInstance(staticfiles_storage, ManifestStaticFilesStorage)
 
+    @ignore_warnings(category=RemovedInDjango51Warning)
+    def test_staticfiles_storage(self):
+        with self.settings(
+            STORAGES={
+                STATICFILES_STORAGE_ALIAS: {
+                    "BACKEND": (
+                        "django.contrib.staticfiles.storage.ManifestStaticFilesStorage"
+                    )
+                }
+            }
+        ):
+            self.assertEqual(
+                settings.STATICFILES_STORAGE,
+                "django.contrib.staticfiles.storage.ManifestStaticFilesStorage",
+            )
+            self.assertIsInstance(
+                storages[STATICFILES_STORAGE_ALIAS],
+                ManifestStaticFilesStorage,
+            )
+
 
 class DefaultStorageDeprecationTests(TestCase):
     msg = DEFAULT_FILE_STORAGE_DEPRECATED_MSG
@@ -118,8 +166,30 @@ class DefaultStorageDeprecationTests(TestCase):
         settings_module.DEFAULT_FILE_STORAGE = "django.core.files.storage.Storage"
         sys.modules["fake_settings_module"] = settings_module
         try:
-            with self.assertRaisesMessage(RemovedInDjango51Warning, self.msg):
-                Settings("fake_settings_module")
+            with self.assertWarnsMessage(RemovedInDjango51Warning, self.msg):
+                fake_settings = Settings("fake_settings_module")
+            self.assertEqual(
+                fake_settings.STORAGES[DEFAULT_STORAGE_ALIAS],
+                {"BACKEND": "django.core.files.storage.Storage"},
+            )
+        finally:
+            del sys.modules["fake_settings_module"]
+
+    def test_settings_storages_init(self):
+        settings_module = ModuleType("fake_settings_module")
+        settings_module.USE_TZ = True
+        settings_module.STORAGES = {
+            DEFAULT_STORAGE_ALIAS: {
+                "BACKEND": "django.core.files.storage.Storage",
+            }
+        }
+        sys.modules["fake_settings_module"] = settings_module
+        try:
+            fake_settings = Settings("fake_settings_module")
+            self.assertEqual(
+                fake_settings.DEFAULT_FILE_STORAGE,
+                "django.core.files.storage.Storage",
+            )
         finally:
             del sys.modules["fake_settings_module"]
 
@@ -163,3 +233,18 @@ class DefaultStorageDeprecationTests(TestCase):
             self.assertIsInstance(storages[DEFAULT_STORAGE_ALIAS], Storage)
             self.assertIsInstance(empty_storages[DEFAULT_STORAGE_ALIAS], Storage)
             self.assertIsInstance(default_storage, Storage)
+
+    @ignore_warnings(category=RemovedInDjango51Warning)
+    def test_default_file_storage(self):
+        with self.settings(
+            STORAGES={
+                DEFAULT_STORAGE_ALIAS: {
+                    "BACKEND": "django.core.files.storage.Storage",
+                }
+            }
+        ):
+            self.assertEqual(
+                settings.DEFAULT_FILE_STORAGE,
+                "django.core.files.storage.Storage",
+            )
+            self.assertIsInstance(storages[DEFAULT_STORAGE_ALIAS], Storage)