diff --git a/cubesatsim/cubesatsim.ino b/cubesatsim/cubesatsim.ino
index 0399f554..0ee353a7 100644
--- a/cubesatsim/cubesatsim.ino
+++ b/cubesatsim/cubesatsim.ino
@@ -2081,7 +2081,8 @@ void start_payload() {
 
 void read_payload()
 {
-
+  payload_str[0] = '\0';  // clear the payload string
+	
 //  if ((Serial.available() > 0)|| first_time == true) 
   {
     blink(50);