diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index 7252563..a0f42d5 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -621,7 +621,7 @@
     return 0;
 }
 
-static int add_ast_fields()
+static int add_ast_fields(void)
 {
     PyObject *empty_tuple, *d;
     if (PyType_Ready(&AST_type) < 0)