diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index c36d239..bb56c7d 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -657,6 +657,12 @@ proxy_iternext(PyWeakReference *proxy)
         return NULL;
 
     PyObject *obj = PyWeakref_GET_OBJECT(proxy);
+    if (!PyIter_Check(obj)) {
+        PyErr_Format(PyExc_TypeError,
+            "Weakref proxy referenced a non-iterator '%.200s' object",
+            Py_TYPE(obj)->tp_name);
+        return NULL;
+    }
     Py_INCREF(obj);
     PyObject* res = PyIter_Next(obj);
     Py_DECREF(obj);