--- a/src/mobility/helper/ns2-mobility-helper.cc	Wed Dec 14 18:50:28 2011 +0300
+++ b/src/mobility/helper/ns2-mobility-helper.cc	Wed Dec 14 19:00:11 2011 +0300
@@ -642,6 +642,10 @@
       // first calculate the time; time = distance / speed
       double time = sqrt (pow (xFinalPosition - retval.m_finalPosition.x, 2) + pow (yFinalPosition - retval.m_finalPosition.y, 2)) / speed;
       NS_LOG_DEBUG ("at=" << at << " time=" << time);
+      if (time == 0)
+        {
+          return retval;
+        }
       // now calculate the xSpeed = distance / time
       double xSpeed = (xFinalPosition - retval.m_finalPosition.x) / time;
       double ySpeed = (yFinalPosition - retval.m_finalPosition.y) / time; // & same with ySpeed
@@ -653,10 +657,7 @@
       NS_LOG_DEBUG ("Calculated Speed: X=" << xSpeed << " Y=" << ySpeed << " Z=" << zSpeed);
 
       // Set the Values
-      if (time >= 0)
-        {
-          Simulator::Schedule (Seconds (at), &ConstantVelocityMobilityModel::SetVelocity, model, Vector (xSpeed, ySpeed, zSpeed));
-        }
+      Simulator::Schedule (Seconds (at), &ConstantVelocityMobilityModel::SetVelocity, model, Vector (xSpeed, ySpeed, zSpeed));
       retval.m_stopEvent = Simulator::Schedule (Seconds (at + time), &ConstantVelocityMobilityModel::SetVelocity, model, Vector (0, 0, 0));
       retval.m_finalPosition.x += xSpeed * time;
       retval.m_finalPosition.y += ySpeed * time;

--- a/src/mobility/test/ns2-mobility-helper-test-suite.cc	Wed Dec 14 18:50:28 2011 +0300
+++ b/src/mobility/test/ns2-mobility-helper-test-suite.cc	Wed Dec 14 19:00:11 2011 +0300
@@ -439,6 +439,17 @@
     //                     id  t  position         velocity
     t->AddReferencePoint ("0", 0, Vector (10, 0, 0), Vector (0,  0, 0));
     AddTestCase (t);
+    t = new Ns2MobilityHelperTest ("Bug 1301 testcase", Seconds (16));
+    t->SetTrace ("$node_(0) set X_ 10.0\n"
+                 "$node_(0) set Y_ 0.0\n"
+                 "$ns_ at 1.0 \"$node_(0) setdest 10  0       1\"\n"
+                 );
+    //                     id  t  position         velocity
+    // Moving to the current position must change nothing. No NaN
+    // speed must be.
+    t->AddReferencePoint ("0", 0, Vector (10, 0, 0), Vector (0,  0, 0));
+    AddTestCase (t);
+
 
   }
 } g_ns2TransmobilityHelperTestSuite;