diff --git a/libraries/GCS_MAVLink/GCS_serial_control.cpp b/libraries/GCS_MAVLink/GCS_serial_control.cpp
index 3ca0c0e383..95cad697a3 100644
--- a/libraries/GCS_MAVLink/GCS_serial_control.cpp
+++ b/libraries/GCS_MAVLink/GCS_serial_control.cpp
@@ -126,6 +126,7 @@ more_data:
 
     // read any reply data
     packet.count = 0;
+    memset(packet.data, 0, sizeof(packet.data))
     while (available > 0) {
         packet.data[packet.count++] = (uint8_t)port->read();
         available--;