diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 9c8701a..eff03c7 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -2236,7 +2236,7 @@ defdict_init(PyObject *self, PyObject *args, PyObject *kwds)
 }
 
 PyDoc_STRVAR(defdict_doc,
-"defaultdict(default_factory[, ...]) --> dict with default factory\n\
+"defaultdict(default_factory=None, /, [...]) --> dict with default factory\n\
 \n\
 The default factory is called without arguments to produce\n\
 a new value when a key is not present, in __getitem__ only.\n\