$OpenBSD$
--- include/osg/Math.orig	Wed Aug 31 12:53:34 2011
+++ include/osg/Math	Wed Aug 31 12:54:04 2011
@@ -18,6 +18,8 @@
 
 #include <osg/Export>
 
+#include <cmath>
+
 //certain math functions were not defined until 10.2
 //so this code checks the version so it can add in workarounds for older versions.
 #ifdef __APPLE__
@@ -207,7 +209,7 @@ inline double round(double v) { return v>=0.0?floor(v+
     inline bool isNaN(float v) { return _isnan(v)!=0; }
     inline bool isNaN(double v) { return _isnan(v)!=0; }
 #else
-    #if defined(__APPLE__)
+    #if defined(__APPLE__) || defined(__OpenBSD__)
         inline bool isNaN(float v) { return std::isnan(v); }
         inline bool isNaN(double v) { return std::isnan(v); }
     #else