How to reproduce the leak:

cd nofib/real/veritas
ghci +RTS -S
Prelude> :load Main
*Main> System.Mem.performGC
 10554832  32639712  38824584  0.048  0.058    2.317    8.386    0    0  (Gen:  1)

Live data is ~38Mb (3rd number). Now unload everything:

*Main> :load
Prelude> System.Mem.performGC
  4005376  32681280  38850224  0.013  0.048    2.330   29.896    0    0  (Gen:  1)

Note the live data didn't go down.

Load the program again:

Prelude> :load Main
...
*Main> System.Mem.performGC
 16344112  47790304  54799632  0.070  0.074    4.343   82.235    0    0  (Gen:  1)

Note the live memory is almost 2x what it was before.