Panici:
I agree with the diode suggestion. Better safe then sorry.
Suggestions for a suitable one?
I'd go with a Schottky type, for a lower turn-on voltage, with a reverse voltage rating over 50 VDC. The current rating isn't important if you are using the circuit dc42 suggested, it would allow you to use a small signal diode like the 1N5711. During normal conditions the current flow will be a small fraction of the 15 mA maximum current rating, so the diode will only fail if something goes very wrong.