diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index cabc666..4a999d1 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -615,7 +615,7 @@
     return 0;
 }
 
-static int add_ast_fields()
+static int add_ast_fields(void)
 {
     PyObject *empty_tuple, *d;
     if (PyType_Ready(&AST_type) < 0)