HTU21D sensors value 999

I tried to use the code example given for HTU21D sensors but the values are always 999, if this is a CRC problem how do I fix it or does it mean that my sensor is broken?

This is the following code :
/*
HTU21D Humidity Sensor Example Code
By: Nathan Seidle
SparkFun Electronics
Date: September 15th, 2013
License: This code is public domain but you buy me a beer if you use this and we meet someday (Beerware license).

Uses the HTU21D library to display the current humidity and temperature

Open serial monitor at 9600 baud to see readings. Errors 998 if not sensor is detected. Error 999 if CRC is bad.

Hardware Connections (Breakoutboard to Arduino):
-VCC = 3.3V
-GND = GND
-SDA = A4 (use inline 330 ohm resistor if your board is 5V)
-SCL = A5 (use inline 330 ohm resistor if your board is 5V)

*/

#include <Wire.h>
#include "SparkFunHTU21D.h"

//Create an instance of the object
HTU21D myHumidity;

void setup()
{
Serial.begin(9600);
Serial.println("HTU21D Example!");

myHumidity.begin();
}

void loop()
{
float humd = myHumidity.readHumidity();
float temp = myHumidity.readTemperature();

Serial.print("Time:");
Serial.print(millis());
Serial.print(" Temperature:");
Serial.print(temp, 1);
Serial.print("C");
Serial.print(" Humidity:");
Serial.print(humd, 1);
Serial.print("%");

Serial.println();
delay(1000);
}

999 means bad CRC. Most probably a hardware problem but you failed to tell us anything about the hardware so you're the only one who's able to fix this.