diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
index 46688a3084f..01597015c2b 100755
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -824,7 +824,7 @@ static int obj2ast_bool(PyObject* obj, bool* out, PyArena* arena)
     return 0;
 }
 
-static int add_ast_fields()
+static int add_ast_fields(void)
 {
     PyObject *empty_tuple, *d;
     if (PyType_Ready(&AST_type) < 0)
diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index cabc66639b6..4a999d12f4c 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -615,7 +615,7 @@ static int obj2ast_bool(PyObject* obj, bool* out, PyArena* arena)
     return 0;
 }
 
-static int add_ast_fields()
+static int add_ast_fields(void)
 {
     PyObject *empty_tuple, *d;
     if (PyType_Ready(&AST_type) < 0)