Higher voltage level on AnalogIN than AREF or intREF

Hallo,

I want to measure analog signals with an ATMega328.
For a better use of measurement range,
I switch to external reference and connect the AREF pin to a voltage 
lower then 5 V (e.g. 1.1 V).
The analog signal is from a RTD.
The RTD is fed by a constant current source.
For normal conditions all is fine.
But if the RTD is damaged (resistance grow up like open RDT connection 
line),
the constant current source rise up to a maximum value of 2.5 V.
Is that a problem for the ATMega, if on the analog IN is a voltage level 
higher than the voltage an AREF pin?

additional question:
Same question but in case of use the internal reference (like in ATMega 
2560).

Thank you.