The circuit you show may work in some conditions but is bad in general.
By depending on the internal protection network to clamp the voltages you can get unwanted and larger than anticipated leakage currents out of adjacent (on the die) pins. This can cause problems with high impedance digital or moderate impedance analog inputs (think about how many uA would cause 1 LSB error on an ADC). The long term reliability can also be questioned.
A Schottky clamp to Vdd is an easy way to deal with that (make sure that there is enough current draw Vdd that the current of all 12V inputs high does not raise Vdd out of regulation- note that this is also true when you use your circuit- there's a hidden path inside the chip to Vdd.
A suitable part number is BAT54A (you get two diodes per SOT-23).