diff --git a/Misc/NEWS b/Misc/NEWS
index b631fde8e52e0d..0fed99b5e7808f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.6.1 release candidate 1?
 Core and Builtins
 -----------------
 
+- bpo-29347: Fixed possibly dereferencing undefined pointers
+  when creating weakref objects.
+
 - bpo-29438: Fixed use-after-free problem in key sharing dict.
 
 - Issue #29319: Prevent RunMainFromImporter overwriting sys.path[0].
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index ab6b23525552b8..9ca386da2563cb 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -24,6 +24,8 @@ init_weakref(PyWeakReference *self, PyObject *ob, PyObject *callback)
 {
     self->hash = -1;
     self->wr_object = ob;
+    self->wr_prev = NULL;
+    self->wr_next = NULL;
     Py_XINCREF(callback);
     self->wr_callback = callback;
 }