Gm+ Chord!?

Hi I have just signed up and need help.

I have a chord chart for ' I'll Remember April' by Don Ray, Gene de Paul and Pat Johnson. I was given it a few years back by an old guitar teacher who was a big Django Reinhardt fan. One of the chords though is Gm+! Is there such a chord?

I am sure someone here can help me as it as kept me awake at night trying to work it out.