AFP build fails

$ head afp-2013-03-02/ROOTS
AVL-Trees
Abortable_Linearizable_Modules
Abstract-Hoare-Logics
Abstract-Rewriting
ArrowImpossibilityGS
AutoFocus-Stream
BDD
BinarySearchTree
Binomial-Heaps
Binomial-Queues
$ cat afp-2013-03-02/ROOTS | grep Dijkstra_Shortest_Path
Dijkstra_Shortest_Path
$ isabelle build -d afp-2013-03-02 -o document=pdf -v Dijkstra_Shortest_Path
### Cannot execute Poly/ML in 32bit mode (missing shared libraries for C/C++)
### Using bulky 64bit version of Poly/ML instead
Started at Thu Mar  7 18:40:53 CET 2013 (polyml-5.5.0_x86_64-linux on thinkcorny)
ISABELLE_BUILD_OPTIONS=""

ML_PLATFORM="x86_64-linux"
ML_HOME="/home/corny/Isabelle2013/contrib/polyml-5.5.0-3/x86_64-linux"
ML_SYSTEM="polyml-5.5.0"
ML_OPTIONS="-H 1000"

Bad session root directory: "afp-2013-03-02"
Finished at Thu Mar  7 18:40:54 CET 2013
0:00:01 elapsed time, 0:00:01 cpu time
$ echo $?
2