Addition: Commit 86f8f5d94e484745b4e406d5410168e7d131d92c / 45928 introduces a slightly different version of the bug. The stack is a little different but it also finally crashes at ":load_panel_subclass". The reported form of the bug starts at commit 39a65664265525fcd7ca23c5613f832b0889cd01 / 50206. ���https://github.com/ruby/ruby/commit/39a65664265525fcd7ca23c5613f832b0889cd01 ���https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=50206 Looks like this is a problem in the files vm.c, vm_core.h and vm_insnhelper.c, which sounds a lot like memory management!?