diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 97a94a76409..856a4a5f386 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -2093,8 +2093,10 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
                  PyUnicode_CompareWithASCIIString(tmp, "__weakref__") == 0))
                 continue;
             tmp =_Py_Mangle(name, tmp);
-            if (!tmp)
+            if (!tmp) {
+                Py_DECREF(newslots);
                 goto bad_slots;
+            }
             PyList_SET_ITEM(newslots, j, tmp);
             j++;
         }