diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 2de9bcd2..81906f43 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -708,7 +708,7 @@ protected:
 
 private:
     handle obj;
-    PyObject *key, *value;
+    PyObject *key = nullptr, *value = nullptr;
     ssize_t pos = -1;
 };
 NAMESPACE_END(iterator_policies)