diff --git a/stubs/cffi/cffi/api.pyi b/stubs/cffi/cffi/api.pyi
index e3ae14188..770751128 100644
--- a/stubs/cffi/cffi/api.pyi
+++ b/stubs/cffi/cffi/api.pyi
@@ -25,7 +25,12 @@ class FFI:
     def __init__(self, backend: types.ModuleType | None = None) -> None: ...
     def cdef(self, csource: str, override: bool = False, packed: bool = False, pack: int | None = None) -> None: ...
     def embedding_api(self, csource: str, packed: bool = False, pack: bool | int | None = None) -> None: ...
-    def dlopen(self, name: str, flags: int = 0) -> _cffi_backend.Lib: ...
+
+    if sys.platform == "win32":
+        def dlopen(self, name: str, flags: int = ...) -> _cffi_backend.Lib: ...
+    else:
+        def dlopen(self, name: str | None, flags: int = ...) -> _cffi_backend.Lib: ...
+
     def dlclose(self, lib: _cffi_backend.Lib) -> None: ...
     def typeof(self, cdecl: str | CData | types.BuiltinFunctionType | types.FunctionType) -> CType: ...
     def sizeof(self, cdecl: str | CData) -> int: ...