diff --git a/src/machine/machine_atmega.go b/src/machine/machine_atmega.go
index 3a73028c5d..81a47c0dfa 100644
--- a/src/machine/machine_atmega.go
+++ b/src/machine/machine_atmega.go
@@ -97,7 +97,7 @@ func (i2c *I2C) stop() {
 }
 
 // writeByte writes a single byte to the I2C bus.
-func (i2c *I2C) writeByte(data byte) {
+func (i2c *I2C) writeByte(data byte) error {
 	// Write data to register.
 	avr.TWDR.Set(data)
 
@@ -107,6 +107,7 @@ func (i2c *I2C) writeByte(data byte) {
 	// Wait till data is transmitted.
 	for !avr.TWCR.HasBits(avr.TWCR_TWINT) {
 	}
+	return nil
 }
 
 // readByte reads a single byte from the I2C bus.
diff --git a/src/machine/machine_fe310.go b/src/machine/machine_fe310.go
index efe94cbe47..8bd4661f4c 100644
--- a/src/machine/machine_fe310.go
+++ b/src/machine/machine_fe310.go
@@ -111,11 +111,12 @@ func (uart *UART) handleInterrupt(interrupt.Interrupt) {
 	uart.Receive(c)
 }
 
-func (uart *UART) writeByte(c byte) {
+func (uart *UART) writeByte(c byte) error {
 	for sifive.UART0.TXDATA.Get()&sifive.UART_TXDATA_FULL != 0 {
 	}
 
 	sifive.UART0.TXDATA.Set(uint32(c))
+	return nil
 }
 
 // SPI on the FE310. The normal SPI0 is actually a quad-SPI meant for flash, so it is best
diff --git a/src/machine/machine_k210.go b/src/machine/machine_k210.go
index 22dc2883ef..e8a304c850 100644
--- a/src/machine/machine_k210.go
+++ b/src/machine/machine_k210.go
@@ -392,11 +392,12 @@ func (uart *UART) handleInterrupt(interrupt.Interrupt) {
 	uart.Receive(c)
 }
 
-func (uart *UART) writeByte(c byte) {
+func (uart *UART) writeByte(c byte) error {
 	for uart.Bus.TXDATA.Get()&kendryte.UARTHS_TXDATA_FULL != 0 {
 	}
 
 	uart.Bus.TXDATA.Set(uint32(c))
+	return nil
 }
 
 func (uart *UART) flush() {}