diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 5080a5b..f8b3783 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -1595,7 +1595,7 @@
             newdefault = PyTuple_GET_ITEM(args, 0);
             if (!PyCallable_Check(newdefault) && newdefault != Py_None) {
                 PyErr_SetString(PyExc_TypeError,
-                    "first argument must be callable");
+                    "first argument must be callable or None");
                 return -1;
             }
         }