diff --git a/src/mobility/model/gauss-markov-mobility-model.cc b/src/mobility/model/gauss-markov-mobility-model.cc
index 897cefcf2..da10f4c99 100644
--- a/src/mobility/model/gauss-markov-mobility-model.cc
+++ b/src/mobility/model/gauss-markov-mobility-model.cc
@@ -168,7 +168,7 @@ GaussMarkovMobilityModel::DoWalk (Time delayLeft)
       if (nextPosition.x > m_bounds.xMax || nextPosition.x < m_bounds.xMin) 
         {
           speed.x = -speed.x;
-          m_meanDirection = 3.14159265 - m_meanDirection;
+          m_meanDirection = M_PI - m_meanDirection;
         }
 
       if (nextPosition.y > m_bounds.yMax || nextPosition.y < m_bounds.yMin) 
diff --git a/src/mobility/model/random-direction-2d-mobility-model.cc b/src/mobility/model/random-direction-2d-mobility-model.cc
index 66b5a4183..f8ca6b92e 100644
--- a/src/mobility/model/random-direction-2d-mobility-model.cc
+++ b/src/mobility/model/random-direction-2d-mobility-model.cc
@@ -29,8 +29,6 @@ namespace ns3 {
 
 NS_LOG_COMPONENT_DEFINE ("RandomDirection2dMobilityModel");
 
-const double RandomDirection2dMobilityModel::PI = 3.14159265358979323846;
-
 NS_OBJECT_ENSURE_REGISTERED (RandomDirection2dMobilityModel);
 
 
@@ -78,7 +76,7 @@ RandomDirection2dMobilityModel::DoInitialize (void)
 void
 RandomDirection2dMobilityModel::DoInitializePrivate (void)
 {
-  double direction = m_direction->GetValue (0, 2 * PI);
+  double direction = m_direction->GetValue (0, 2 * M_PI);
   SetDirectionAndSpeed (direction);
 }
 
@@ -115,20 +113,20 @@ RandomDirection2dMobilityModel::SetDirectionAndSpeed (double direction)
 void
 RandomDirection2dMobilityModel::ResetDirectionAndSpeed (void)
 {
-  double direction = m_direction->GetValue (0, PI);
+  double direction = m_direction->GetValue (0, M_PI);
 
   m_helper.UpdateWithBounds (m_bounds);
   Vector position = m_helper.GetCurrentPosition ();
   switch (m_bounds.GetClosestSide (position))
     {
     case Rectangle::RIGHT:
-      direction += PI / 2;
+      direction += M_PI / 2;
       break;
     case Rectangle::LEFT:
-      direction += -PI / 2;
+      direction += -M_PI / 2;
       break;
     case Rectangle::TOP:
-      direction += PI;
+      direction += M_PI;
       break;
     case Rectangle::BOTTOM:
       direction += 0.0;
diff --git a/src/mobility/model/random-direction-2d-mobility-model.h b/src/mobility/model/random-direction-2d-mobility-model.h
index 617ab2bd4..df525a571 100644
--- a/src/mobility/model/random-direction-2d-mobility-model.h
+++ b/src/mobility/model/random-direction-2d-mobility-model.h
@@ -60,7 +60,6 @@ private:
   virtual Vector DoGetVelocity (void) const;
   virtual int64_t DoAssignStreams (int64_t);
 
-  static const double PI;
   Ptr<UniformRandomVariable> m_direction;
   Rectangle m_bounds;
   Ptr<RandomVariableStream> m_speed;
diff --git a/src/wifi/model/dsss-error-rate-model.cc b/src/wifi/model/dsss-error-rate-model.cc
index 353c91bad..06c5f40b5 100644
--- a/src/wifi/model/dsss-error-rate-model.cc
+++ b/src/wifi/model/dsss-error-rate-model.cc
@@ -35,7 +35,7 @@ double
 DsssErrorRateModel::DqpskFunction (double x)
 {
   NS_LOG_FUNCTION_NOARGS ();
-  return ((std::sqrt (2.0) + 1.0) / std::sqrt (8.0 * 3.1415926 * std::sqrt (2.0)))
+  return ((std::sqrt (2.0) + 1.0) / std::sqrt (8.0 * M_PI * std::sqrt (2.0)))
     * (1.0 / std::sqrt (x)) * std::exp ( -(2.0 - std::sqrt (2.0)) * x);
 }