--- a/src/util/math.h	2015-12-29 17:10:41.000000000 +0100
+++ b/src/util/math.h	2016-09-25 12:54:18.345291146 +0200
@@ -3,8 +3,20 @@
 
 // Causes MSVC to define M_PI and friends.
 // http://msdn.microsoft.com/en-us/library/4hwaceh6.aspx
+// Our SConscript defines this but check anyway.
+#ifdef __WINDOWS__
+#ifndef _USE_MATH_DEFINES
 #define _USE_MATH_DEFINES
-#include <cmath>
+#endif
+#endif
+
+#include <math.h>
+#include <cmath> 
+// Note: Because of our fpclassify hack, we actualy need to inlude both, 
+// the c and the c++ version of the math header.  
+// From GCC 6.1.1 math.h depends on cmath, which failes to compile if included 
+// after our fpclassify hack 
+
 #include <algorithm>
 
 #include "util/assert.h"