On a clean image from get.pharo.org/64/
Attempting to load the following repository

Metacello new
�� baseline: 'WillowBootstrap';
�� repository: 'github://ba-st/Willow-Bootstrap:master/source';
�� load.

Consistently causes a VM crash (crash.dump in attatchment).

This does not happen with the 32 bit image.

Image + VM details

Image
-----
/home/jmaestri/Pharo/workspace/Pharo.image
Pharo6.0
Latest update: #60510
Unnamed
Virtual Machine
---------------
/home/jmaestri/Pharo/workspace/pharo-vm/lib/pharo/5.0-201707201942/pharo
CoInterpreter VMMaker.oscog-eem.2254 uuid: 4f2c2cce-f4a2-469a-93f1-97ed941df0ad Jul 20 2017
StackToRegisterMappingCogit VMMaker.oscog-eem.2252 uuid: 2f3e9b0e-ecd3-4adf-b092-cce2e2587a5c Jul 20 2017
VM: 201707201942 https://github.com/OpenSmalltalk/opensmalltalk-vm.git $ Date: Thu Jul 20 12:42:21 2017 -0700 $ Plugins: 201707201942 https://github.com/OpenSmalltalk/opensmalltalk-vm.git $
Unix built on Jul 20 2017 20:40:36 Compiler: 4.6.3
VMMaker versionString VM: 201707201942 https://github.com/OpenSmalltalk/opensmalltalk-vm.git $ Date: Thu Jul 20 12:42:21 2017 -0700 $ Plugins: 201707201942 https://github.com/OpenSmalltalk/opensmalltalk-vm.git $
CoInterpreter VMMaker.oscog-eem.2254 uuid: 4f2c2cce-f4a2-469a-93f1-97ed941df0ad Jul 20 2017
StackToRegisterMappingCogit VMMaker.oscog-eem.2252 uuid: 2f3e9b0e-ecd3-4adf-b092-cce2e2587a5c Jul 20 2017