diff --git a/hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_si2c.c b/hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_si2c.c
index e53707df7..29149aa09 100644
--- a/hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_si2c.c
+++ b/hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_si2c.c
@@ -131,7 +131,7 @@ static bool twi_write_byte(unsigned char byte) {
     twi_write_bit(byte & 0x80);
     byte <<= 1;
   }
-  return twi_read_bit();//NACK/ACK
+  return !twi_read_bit();//NACK/ACK
 }
 
 static unsigned char twi_read_byte(bool nack) {