Index: firmware/App/Services/SystemComm.c
===================================================================
diff -u -rd830f37cf6a42a16399c87985bd51dfd9312ced3 -r1375b56bfeb3f458644484d9fe4f2e75e1289e38
--- firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision d830f37cf6a42a16399c87985bd51dfd9312ced3)
+++ firmware/App/Services/SystemComm.c	(.../SystemComm.c)	(revision 1375b56bfeb3f458644484d9fe4f2e75e1289e38)
@@ -747,7 +747,7 @@
             // if a minimum sized msg would fit in remaining, continue
             if ( remSize >= MESSAGE_OVERHEAD_SIZE )
             {
-                payloadSize = data[ pos + sizeof( U16 ) + sizeof( U16) ];
+                payloadSize = data[ pos + sizeof(MESSAGE_HEADER_T) - sizeof(U08) ];
                 msgSize = MESSAGE_OVERHEAD_SIZE + payloadSize;
                 // we now know the size of the message - we can now know if full message is contained in buffer
                 if ( msgSize <= remSize )