Index: mttroot/mtt/cc/include/useful-functions.hh
==================================================================
--- mttroot/mtt/cc/include/useful-functions.hh
+++ mttroot/mtt/cc/include/useful-functions.hh
@@ -22,15 +22,19 @@
 #include <cmath>
 #define cast_to_double	static_cast<double>
 using std::pow;
 #endif /* ! __cplusplus */
 
-
+#ifdef M_PI
 static double pi = M_PI;
 static double Pi = M_PI;
 static double PI = M_PI;
-
+#else
+static double pi = 3.1416;
+static double Pi = pi;
+static double PI = pi;
+#endif
 
 static inline double
 max (const double x1, const double x2)
 {
   return cast_to_double ((x1 >= x2) ? x1 : (x1 < x2) ? x2 : 0);