diff --git a/stdlib/2and3/optparse.pyi b/stdlib/2and3/optparse.pyi
index 64f3fb669..359134197 100644
--- a/stdlib/2and3/optparse.pyi
+++ b/stdlib/2and3/optparse.pyi
@@ -165,6 +165,7 @@ class Values:
     def read_file(self, filename: _Text, mode: _Text) -> None: ...
     def read_module(self, modname: _Text, mode: _Text) -> None: ...
     def __getattr__(self, name: str) -> Any: ...
+    def __setattr__(self, name: str, value: Any) -> None: ...
 
 class OptionParser(OptionContainer):
     allow_interspersed_args = ...  # type: bool