diff --git a/hardware/arduino/cores/arduino/CDC.cpp b/hardware/arduino/cores/arduino/CDC.cpp
index 1ee3a488a..701e48398 100644
--- a/hardware/arduino/cores/arduino/CDC.cpp
+++ b/hardware/arduino/cores/arduino/CDC.cpp
@@ -141,16 +141,22 @@ void Serial_::end(void)
 void Serial_::accept(void) 
 {
 	ring_buffer *buffer = &cdc_rx_buffer;
-	int c = USB_Recv(CDC_RX); 
 	int i = (unsigned int)(buffer->head+1) % SERIAL_BUFFER_SIZE;
 	
 	// if we should be storing the received character into the location
 	// just before the tail (meaning that the head would advance to the
 	// current location of the tail), we're about to overflow the buffer
 	// and so we don't write the character or advance the head.
-	if (i != buffer->tail) {
+
+	// while we have room to store a byte
+	while (i != buffer->tail) {
+		int c = USB_Recv(CDC_RX);
+		if (c == -1)
+			break;	// no more data
 		buffer->buffer[buffer->head] = c;
 		buffer->head = i;
+
+		i = (unsigned int)(buffer->head+1) % SERIAL_BUFFER_SIZE;
 	}
 }
 
diff --git a/hardware/arduino/cores/arduino/USBCore.cpp b/hardware/arduino/cores/arduino/USBCore.cpp
index 6766be61a..8bcf66c54 100644
--- a/hardware/arduino/cores/arduino/USBCore.cpp
+++ b/hardware/arduino/cores/arduino/USBCore.cpp
@@ -603,7 +603,7 @@ ISR(USB_GEN_vect)
 	{
 #ifdef CDC_ENABLED
 		USB_Flush(CDC_TX);				// Send a tx frame if found
-		while (USB_Available(CDC_RX))	// Handle received bytes (if any)
+		if (USB_Available(CDC_RX))	// Handle received bytes (if any)
 			Serial.accept();
 #endif