diff --git a/Python/ast.c b/Python/ast.c
index 3440308..df2c63d 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -532,8 +532,9 @@
 {
     _Py_IDENTIFIER(normalize);
     PyObject* id = PyUnicode_DecodeUTF8(n, strlen(n), NULL);
-    if (!id || PyUnicode_READY(id) == -1)
+    if (!id)
         return NULL;
+    assert(PyUnicode_IS_READY(id));
     /* Check whether there are non-ASCII characters in the
        identifier; if so, normalize to NFKC. */
     if (PyUnicode_MAX_CHAR_VALUE((PyUnicodeObject *)id) >= 128) {