From 9b880ba743a39b35cfa3b806a96c5f99428d7c2b Mon Sep 17 00:00:00 2001
From: Wenzel Jakob <wenzel.jakob@epfl.ch>
Date: Mon, 25 Apr 2016 03:25:13 +0200
Subject: [PATCH] keep_alive: don't fail when there is no patient

---
 include/pybind11/pybind11.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index f653ba97f..e93139200 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -982,6 +982,9 @@ PYBIND11_NOINLINE inline void keep_alive_impl(int Nurse, int Patient, handle arg
     if (!nurse || !patient)
         pybind11_fail("Could not activate keep_alive!");
 
+    if (patient.ptr() == Py_None)
+        return; /* Nothing to keep alive */
+
     cpp_function disable_lifesupport(
         [patient](handle weakref) { patient.dec_ref(); weakref.dec_ref(); });