diff --git a/PyGreSQL-5.0.3-python-3.6.patch b/PyGreSQL-5.0.3-python-3.6.patch
new file mode 100644
index 0000000..20ba7a8
--- /dev/null
+++ b/PyGreSQL-5.0.3-python-3.6.patch
@@ -0,0 +1,28 @@
+From 7fe2cc4d84d37e29f256fd8f614861121a2da254 Mon Sep 17 00:00:00 2001
+From: Christoph Zwerschke <cito@online.de>
+Date: Fri, 6 Jan 2017 16:36:05 +0000
+Subject: [PATCH] Fix an issue with Python 3.6
+
+While running over a dictionary in a for loop, we altered its values.
+This used to work perfectly well in Python before 3.6, but now causes
+problems, probably due to internal optimizations. We avoid this now.
+---
+ pg.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/pg.py b/pg.py
+index 117e440..5942d50 100644
+--- a/pg.py
++++ b/pg.py
+@@ -708,7 +708,7 @@ class Adapter:
+             # so we first must find the values actually used in the command
+             used_values = {}
+             literals = dict.fromkeys(values, '')
+-            for key in literals:
++            for key in values:
+                 del literals[key]
+                 try:
+                     command % literals
+-- 
+2.9.3
+
diff --git a/PyGreSQL.spec b/PyGreSQL.spec
index 4755ae0..229c4bf 100644
--- a/PyGreSQL.spec
+++ b/PyGreSQL.spec
@@ -5,7 +5,7 @@
 
 Name:		%{srcname}
 Version:	5.0.3
-Release:	3%{?dist}
+Release:	4%{?dist}
 Summary:	%{sum}
 
 Group:		Applications/Databases
@@ -19,6 +19,8 @@ License:	PostgreSQL or Python
 
 Source0:	http://www.pygresql.org/files/PyGreSQL-%{version}.tar.gz
 
+Patch0:		%name-5.0.3-python-3.6.patch
+
 # PyGreSQL was originally shipped as a sub-RPM of the PostgreSQL package;
 # these Provides/Obsoletes give a migration path.  Note there is no
 # intention of changing the version numbers in future.
@@ -106,6 +108,9 @@ EOF
 
 
 %changelog
+* Fri Feb 17 2017 Pavel Raiskup <praiskup@redhat.com> - 5.0.3-4
+- fix nasty undefined behavior (rhbz#1423108)
+
 * Fri Feb 10 2017 Fedora Release Engineering <releng@fedoraproject.org> - 5.0.3-3
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_26_Mass_Rebuild