diff --git a/stdlib/2.7/__builtin__.pyi b/stdlib/2.7/__builtin__.pyi
index 8b0ee5318..901cb6584 100644
--- a/stdlib/2.7/__builtin__.pyi
+++ b/stdlib/2.7/__builtin__.pyi
@@ -835,7 +835,8 @@ class MemoryError(StandardError): ...
 class NameError(StandardError): ...
 class NotImplementedError(RuntimeError): ...
 class OSError(EnvironmentError): ...
-class WindowsError(OSError): ...
+class WindowsError(OSError):
+    winerror = ...  # type: int
 class OverflowError(ArithmeticError): ...
 class ReferenceError(StandardError): ...
 class SyntaxError(StandardError):
diff --git a/stdlib/3/builtins.pyi b/stdlib/3/builtins.pyi
index 16e8c0f4e..541bc1588 100644
--- a/stdlib/3/builtins.pyi
+++ b/stdlib/3/builtins.pyi
@@ -799,7 +799,8 @@ class NotADirectoryError(OSError): ...
 class PermissionError(OSError): ...
 class ProcessLookupError(OSError): ...
 class TimeoutError(OSError): ...
-class WindowsError(OSError): ...
+class WindowsError(OSError):
+    winerror = ...  # type: int
 class OverflowError(ArithmeticError): ...
 class ReferenceError(Exception): ...
 class StopIteration(Exception):