it might sorta fit TIGHT if you push it in, i was able to get a SIG 220 in a M12 holster, fit tight and was able to use the flap.

bianchi makes the UM84III, which is a widebody holster that fits the glocks and sigs better. the M12/UM84 is more of a slim body holster that works for berettas and 1911s.
if you decide to get the M12 holster, SAVE yerself some $$$ money and get the ones made by Cathey Industries (USGI Contractor) for $39, instead of bianchis price of $70. bianchi is the ONLY company making the UM84II and UM84III

best thing to do is go to a gun show with your glock and find the holster and try it out before you buy.

It will fit if it is the same size at the Glock 34. I use this holster to carry my Glock on callouts. The thumbsnap attachment as well as the removeable flap on the holster keep the gun in place.

Karl