diff --git a/tools/python/src/pyassert.h b/tools/python/src/pyassert.h
index 2d6e3e7e1..0c7c0ad7f 100644
--- a/tools/python/src/pyassert.h
+++ b/tools/python/src/pyassert.h
@@ -1,6 +1,9 @@
 // Copyright (C) 2013  Davis E. King (davis@dlib.net)
 // License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_PYaSSERT_H__
+#define DLIB_PYaSSERT_H__
 
+#include <boost/python.hpp>
 
 #define pyassert(_exp,_message)                                             \
     {if ( !(_exp) )                                                         \
@@ -8,3 +11,6 @@
         PyErr_SetString( PyExc_ValueError, _message );                      \
         boost::python::throw_error_already_set();                           \
     }}                                                                      
+
+#endif // DLIB_PYaSSERT_H__
+