--- a/src/spectrum/helper/spectrum-helper.cc	Fri Sep 30 14:25:23 2011 -0700
+++ b/src/spectrum/helper/spectrum-helper.cc	Tue Oct 04 18:40:50 2011 +0200
@@ -215,7 +215,7 @@
   NS_ASSERT (m_channel);
   Ptr<SpectrumPhy> phy = (m_phy.Create ())->GetObject<SpectrumPhy> ();
   phy->SetChannel (m_channel);
-  phy->SetMobility (node);
+  phy->SetMobility (node->GetObject<MobilityModel> ());
   phy->SetDevice (device);
   return phy;
 }