$OpenBSD: patch-setupext_py,v 1.16 2016/11/14 18:55:50 shadchin Exp $
--- setupext.py.orig	Sat Sep 10 00:58:14 2016
+++ setupext.py	Fri Oct  7 02:19:09 2016
@@ -1313,6 +1313,7 @@ class BackendTkAgg(OptionalBackendPackage):
             ]
 
         ext = make_extension('matplotlib.backends._tkagg', sources)
+        ext.include_dirs.extend(['${X11BASE}/include'])
         self.add_flags(ext)
         Numpy().add_flags(ext)
         LibAgg().add_flags(ext, add_sources=False)
