diff --git a/src/mobility/random-direction-2d-mobility-model.cc b/src/mobility/random-direction-2d-mobility-model.cc
index 6c32e57aa..0dde51ee8 100644
--- a/src/mobility/random-direction-2d-mobility-model.cc
+++ b/src/mobility/random-direction-2d-mobility-model.cc
@@ -30,7 +30,7 @@ NS_LOG_COMPONENT_DEFINE ("RandomDirection2dMobilityModel");
 
 namespace ns3 {
 
-const double RandomDirection2dMobilityModel::PI = 3.1415;
+const double RandomDirection2dMobilityModel::PI = 3.14159265358979323846;
 const ClassId RandomDirection2dMobilityModel::cid = 
   MakeClassId<RandomDirection2dMobilityModel> ("RandomDirection2dMobilityModel",
                                                MobilityModel::iid);