The midfielder signed a similar deal in mid-October having worked his way back to fitness from a long-term knee injury despite his contract expiring in the summer.
Mahon has now put pen to paper on new terms which will run until December 17.
The 33-year-old has been struggling with a hamstring problem recently but if he is fit he could be involved in Saturday's match against Preston as regular holding midfielder Shaun Derry is suspended.
Source: PA
Source: PA