Hey, I made some progress on that one. I think, this is what's going on: 1. Two new PedDevice A and B are malloc'ed by the libparted when opening the installer partitioning page. 2. They are added to the %devices weak hash table by pointer->device! and their respective finalizers are registered. 3. The partitioning ends and A goes out of scope. It is eventually removed from %devices but it does not mean its finalizer will be run immediately. 4. The partitioning is restarted using the installer menu. B is still in the %devices hash table. However, A is now gone and is added again to the %devices hash table by the pointer->device! procedure. Another finalizer is registered for A. That's because set-pointer-finalizer! does not *set* a finalizer it *adds* one. 5. The partitioning ends and both A and B goes out of scope. They are removed from %devices and their finalizers are called. The A finalizer is called twice resulting in a double free. This race condition is created by the fact that there is a time window where the device is removed from the %devices hash table but its finalizer is not immediately called. If set-pointer-finalizer! actually called scm_i_set_finalizer instead of scm_i_add_finalizer the A finalizer would be set twice but called only once. Do you think it would be an option? I attached the instrumentation patches (good old printf's) as well as the syslog I based my analysis upon. Thanks, Mathieu