From 511df0f3ebab31042d63def6a18b9a5afee60ed5 Mon Sep 17 00:00:00 2001
From: Elliott Sales de Andrade <quantum.analyst@gmail.com>
Date: Thu, 11 Apr 2019 02:24:54 -0400
Subject: [PATCH] Correctly handle invalid PNG metadata.

---
 src/_png.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/_png.cpp b/src/_png.cpp
index da8f696d7fcc..f40c009d3b1b 100644
--- a/src/_png.cpp
+++ b/src/_png.cpp
@@ -300,7 +300,11 @@ static PyObject *Py_write_png(PyObject *self, PyObject *args, PyObject *kwds)
 
 #ifdef PNG_TEXT_SUPPORTED
     // Save the metadata
-    if (metadata != NULL) {
+    if (metadata != NULL && metadata != Py_None) {
+        if (!PyDict_Check(metadata)) {
+            PyErr_SetString(PyExc_TypeError, "metadata must be a dict or None");
+            goto exit;
+        }
         meta_size = PyDict_Size(metadata);
         text = new png_text[meta_size];