diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index f26602d5871acc..f5679fe3a6f362 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -2067,7 +2067,7 @@ math_trunc(PyObject *module, PyObject *x)
         return PyFloat_Type.tp_as_number->nb_int(x);
     }
 
-    if (_PyType_IsReady(Py_TYPE(x))) {
+    if (!_PyType_IsReady(Py_TYPE(x))) {
         if (PyType_Ready(Py_TYPE(x)) < 0)
             return NULL;
     }