diff --git a/src/machine/machine_k210.go b/src/machine/machine_k210.go
index 243ae54c..ca5f2d80 100644
--- a/src/machine/machine_k210.go
+++ b/src/machine/machine_k210.go
@@ -611,7 +611,7 @@ func (i2c I2C) Tx(addr uint16, w, r []byte) error {
 		di := 0
 
 		for dataLen != 0 || cmdLen != 0 {
-			fifoLen := 8 - i2c.Bus.RXFLR.Get()
+			fifoLen := i2c.Bus.RXFLR.Get()
 			if dataLen < fifoLen {
 				fifoLen = dataLen
 			}