diff --git a/src/csma/model/csma-channel.cc b/src/csma/model/csma-channel.cc
index 7f96b4673..0ba64b537 100644
--- a/src/csma/model/csma-channel.cc
+++ b/src/csma/model/csma-channel.cc
@@ -170,7 +170,7 @@ CsmaChannel::Detach (Ptr<CsmaNetDevice> device)
 }
 
 bool
-CsmaChannel::TransmitStart (Ptr<Packet> p, uint32_t srcId)
+CsmaChannel::TransmitStart (Ptr<const Packet> p, uint32_t srcId)
 {
   NS_LOG_FUNCTION (this << p << srcId);
   NS_LOG_INFO ("UID is " << p->GetUid () << ")");
@@ -188,7 +188,7 @@ CsmaChannel::TransmitStart (Ptr<Packet> p, uint32_t srcId)
     }
 
   NS_LOG_LOGIC ("switch to TRANSMITTING");
-  m_currentPkt = p;
+  m_currentPkt = p->Copy ();
   m_currentSrc = srcId;
   m_state = TRANSMITTING;
   return true;
diff --git a/src/csma/model/csma-channel.h b/src/csma/model/csma-channel.h
index ae4859941..4bbcfd873 100644
--- a/src/csma/model/csma-channel.h
+++ b/src/csma/model/csma-channel.h
@@ -184,7 +184,7 @@ public:
    * \return True if the channel is not busy and the transmitting net
    * device is currently active.
    */
-  bool TransmitStart (Ptr<Packet> p, uint32_t srcId);
+  bool TransmitStart (Ptr<const Packet> p, uint32_t srcId);
 
   /**
    * \brief Indicates that the net device has finished transmitting