diff --git a/Include/floatobject.h b/Include/floatobject.h
index 90f0a45..243914b 100644
--- a/Include/floatobject.h
+++ b/Include/floatobject.h
@@ -113,8 +113,9 @@
 /* Format the object based on the format_spec, as defined in PEP 3101
    (Advanced String Formatting). */
 PyAPI_FUNC(PyObject *) _PyFloat_FormatAdvanced(PyObject *obj,
-					       Py_UNICODE *format_spec,
-					       Py_ssize_t format_spec_len);
+					       PyObject *format_spec,
+					       Py_ssize_t start,
+					       Py_ssize_t end);
 #endif /* Py_LIMITED_API */
 
 #ifdef __cplusplus