diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
index 46688a3..0159701 100755
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -824,7 +824,7 @@
     return 0;
 }
 
-static int add_ast_fields()
+static int add_ast_fields(void)
 {
     PyObject *empty_tuple, *d;
     if (PyType_Ready(&AST_type) < 0)