diff --git a/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java b/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java
index 3fda7681d..946e2398c 100644
--- a/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java
+++ b/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/CC2420RadioPacketConverter.java
@@ -198,7 +198,7 @@ public class CC2420RadioPacketConverter {
     System.arraycopy(data, 6 /* skipping preamble+synch+len */, originalData, 0, originalLen);
     if (len < 0) {
       /*logger.warn("No cross-level conversion available: negative packet length");*/
-      return new ConvertedRadioPacket(new byte[0], originalData);
+      return null;
     }
     byte convertedData[] = new byte[len];
     System.arraycopy(data, pos, convertedData, 0, len);
diff --git a/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/Msp802154Radio.java b/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/Msp802154Radio.java
index c99710f3d..9937e6a74 100644
--- a/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/Msp802154Radio.java
+++ b/tools/cooja/apps/mspsim/src/org/contikios/cooja/mspmote/interfaces/Msp802154Radio.java
@@ -99,6 +99,7 @@ public class Msp802154Radio extends Radio implements CustomDataRadio {
       public void receivedByte(byte data) {
         if (!isTransmitting()) {
           lastEvent = RadioEvent.TRANSMISSION_STARTED;
+          lastOutgoingPacket = null;
           isTransmitting = true;
           len = 0;
           expMpduLen = 0;
@@ -139,10 +140,12 @@ public class Msp802154Radio extends Radio implements CustomDataRadio {
 
         if (((expMpduLen & 0x80) == 0) && len == expMpduLen + 6 && isSynchronized) {
           lastOutgoingPacket = CC2420RadioPacketConverter.fromCC2420ToCooja(buffer);
-          lastEvent = RadioEvent.PACKET_TRANSMITTED;
-          //logger.debug("----- 802.15.4 PACKET TRANSMITTED -----");
-          setChanged();
-          notifyObservers();
+          if (lastOutgoingPacket != null) {
+            lastEvent = RadioEvent.PACKET_TRANSMITTED;
+            //logger.debug("----- 802.15.4 PACKET TRANSMITTED -----");
+            setChanged();
+            notifyObservers();
+          }
           isSynchronized = false;
         }
       }
diff --git a/tools/cooja/java/org/contikios/cooja/motes/AbstractApplicationMote.java b/tools/cooja/java/org/contikios/cooja/motes/AbstractApplicationMote.java
index 98de78327..fd16d37a3 100644
--- a/tools/cooja/java/org/contikios/cooja/motes/AbstractApplicationMote.java
+++ b/tools/cooja/java/org/contikios/cooja/motes/AbstractApplicationMote.java
@@ -76,7 +76,8 @@ public abstract class AbstractApplicationMote extends AbstractWakeupMote impleme
         if (radio.getLastPacketReceived() != null)
             receivedPacket(radio.getLastPacketReceived());
       } else if (radio.getLastEvent() == Radio.RadioEvent.TRANSMISSION_FINISHED) {
-        sentPacket(radio.getLastPacketTransmitted());
+        if (radio.getLastPacketTransmitted() != null)
+            sentPacket(radio.getLastPacketTransmitted());
       }
     }
   };
diff --git a/tools/cooja/java/org/contikios/cooja/plugins/RadioLogger.java b/tools/cooja/java/org/contikios/cooja/plugins/RadioLogger.java
index 17f5417c2..abdc76f6c 100644
--- a/tools/cooja/java/org/contikios/cooja/plugins/RadioLogger.java
+++ b/tools/cooja/java/org/contikios/cooja/plugins/RadioLogger.java
@@ -517,10 +517,12 @@ public class RadioLogger extends VisPlugin {
           return;
         }
         final RadioConnectionLog loggedConn = new RadioConnectionLog();
+        loggedConn.packet = conn.getSource().getLastPacketTransmitted();
+        if (loggedConn.packet == null)
+          return;
         loggedConn.startTime = conn.getStartTime();
         loggedConn.endTime = simulation.getSimulationTime();
         loggedConn.connection = conn;
-        loggedConn.packet = conn.getSource().getLastPacketTransmitted();
         java.awt.EventQueue.invokeLater(new Runnable() {
           @Override
           public void run() {