diff --git a/src/blackmisc/mathematics.h b/src/blackmisc/mathematics.h
index 9105bd9f0..01fc9ebb7 100644
--- a/src/blackmisc/mathematics.h
+++ b/src/blackmisc/mathematics.h
@@ -86,7 +86,7 @@ public:
      */
     static const double &PI2()
     {
-        static double pi2 = PI();
+        static double pi2 = 2.0 * PI();
         return pi2;
     }