I2C between 5v Arduino and 2.5 accelerometer

Hi all,
I am trying to interface between an Arduino Mini and a LIS2de12 accelerometer using I2C. The Arduino operates at 5v and the accelerometer operates at 2.5v but can take up to 3.6v. I am not using pull-up resistor as the ATmega 328 has internal resistors. Would the difference in voltage not allow I2C? If the difference doesn't allow I2C, can this issue be solved by adding pull-up resistors?

Thanks for your help!