Dont put "void" in signature for nullary functions.
diff --git a/Doc/c-api/sys.rst b/Doc/c-api/sys.rst
index f5d2ab0..6788bc9 100644
--- a/Doc/c-api/sys.rst
+++ b/Doc/c-api/sys.rst
@@ -73,7 +73,7 @@
    case *name* is deleted from the sys module. Returns ``0`` on success, ``-1``
    on error.
 
-.. cfunction:: void PySys_ResetWarnOptions(void)
+.. cfunction:: void PySys_ResetWarnOptions()
 
    Reset :data:`sys.warnoptions` to an empty list.