diff --git a/sw/airborne/arch/sim/ivy_transport.h b/sw/airborne/arch/sim/ivy_transport.h
index 8d416e89e9..219e6cafa9 100644
--- a/sw/airborne/arch/sim/ivy_transport.h
+++ b/sw/airborne/arch/sim/ivy_transport.h
@@ -10,7 +10,7 @@ extern char* ivy_p;
 
 #define IvyTransportHeader(_dev,len) ivy_p=ivy_buf;
 
-#define IvyTransportTrailer(_dev) { *ivy_p = '\0'; IvySendMsg("%s",ivy_buf); }
+#define IvyTransportTrailer(_dev) { *(--ivy_p) = '\0'; IvySendMsg("%s",ivy_buf); }
 
 #define IvyTransportPutUint8(_dev,x) { ivy_p += sprintf(ivy_p, "%u ", x); }
 #define IvyTransportPutNamedUint8(_dev,_name, _x) { ivy_p += sprintf(ivy_p, "%s ", _name); }