diff --git a/src/machine/machine_fe310.go b/src/machine/machine_fe310.go
index 8bd4661f4c..85a2c5bd37 100644
--- a/src/machine/machine_fe310.go
+++ b/src/machine/machine_fe310.go
@@ -119,6 +119,8 @@ func (uart *UART) writeByte(c byte) error {
 	return nil
 }
 
+func (uart *UART) flush() {}
+
 // SPI on the FE310. The normal SPI0 is actually a quad-SPI meant for flash, so it is best
 // to use SPI1 or SPI2 port for most applications.
 type SPI struct {