diff --git a/src/attr/__init__.pyi b/src/attr/__init__.pyi
index 758decf8f..ee9f2127f 100644
--- a/src/attr/__init__.pyi
+++ b/src/attr/__init__.pyi
@@ -136,7 +136,7 @@ class Attribute(Generic[_T]):
     type: type[_T] | None
     kw_only: bool
     on_setattr: _OnSetAttrType
-    alias: str | None
+    alias: str
 
     def evolve(self, **changes: Any) -> "Attribute[Any]": ...