diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
index e2a57177d20afb..14fe70000b829a 100755
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -2274,7 +2274,7 @@ def generate_module_def(mod, metadata, f, internal_h):
             PyInterpreterState *interp = _PyInterpreterState_GET();
             struct ast_state *state = &interp->ast;
             assert(!state->finalized);
-            if (_PyOnceFlag_CallOnce(&state->once, (_Py_once_fn_t *)&init_types, state) < 0) {
+            if (_PyOnceFlag_CallOnce(&state->once, &init_types, state) < 0) {
                 return NULL;
             }
             return state;