diff --git a/build/shared/examples/11.ArduinoISP/ArduinoISP/ArduinoISP.ino b/build/shared/examples/11.ArduinoISP/ArduinoISP/ArduinoISP.ino
index 8caa58eabe1..860a3449d86 100644
--- a/build/shared/examples/11.ArduinoISP/ArduinoISP/ArduinoISP.ino
+++ b/build/shared/examples/11.ArduinoISP/ArduinoISP/ArduinoISP.ino
@@ -331,6 +331,9 @@ uint8_t spi_transaction(uint8_t a, uint8_t b, uint8_t c, uint8_t d) {
 
 void empty_reply() {
   if (CRC_EOP == getch()) {
+    // clear RX buffer. No more host data expected until after SYNC.
+    while (SERIAL.available())
+      SERIAL.read();
     SERIAL.print((char)STK_INSYNC);
     SERIAL.print((char)STK_OK);
   } else {