diff --git a/django/conf/__init__.py b/django/conf/__init__.py
index c887890a0c..e16f11e9f9 100644
--- a/django/conf/__init__.py
+++ b/django/conf/__init__.py
@@ -107,7 +107,7 @@ class Settings(BaseSettings):
                 setattr(self, setting, setting_value)
 
         if not self.SECRET_KEY:
-            raise ValueError("The SECRET_KEY setting mustn't be empty.")
+            raise DeprecationWarning("The SECRET_KEY setting must not be empty.")
 
         if hasattr(time, 'tzset') and self.TIME_ZONE:
             # When we can, attempt to validate the timezone. If we can't find