Raises an exception pointing to marshal.cpp:27 - lhs is zero. Sadly this gem is written in C++ and I cannot help in debugging...
#0 0x00000000004bc2ee in operator!= (lhs=..., sym=5307) at /home/dvl/motri/mruby/build/mrbgems/mruby-marshal/src/marshal.cpp:27
#1 0x00000000004bc6fe in (anonymous namespace)::write_context::symbol (this=0x7ffdd62c47f0, sym=5307) at /home/dvl/motri/mruby/build/mrbgems/mruby-marshal/src/marshal.cpp:101
#2 0x00000000004bcba5 in (anonymous namespace)::write_context::class_symbol (this=0x7ffdd62c47f0, v=0x2e18ee0) at /home/dvl/motri/mruby/build/mrbgems/mruby-marshal/src/marshal.cpp:164
#3 0x00000000004bffc6 in (anonymous namespace)::write_context::klass<(char)'o'> (this=0x7ffdd62c47f0, v=..., check=true) at /home/dvl/motri/mruby/build/mrbgems/mruby-marshal/src/marshal.cpp:191
#4 0x00000000004bd439 in (anonymous namespace)::write_context::marshal (this=0x7ffdd62c47f0, v=..., limit=-2) at /home/dvl/motri/mruby/build/mrbgems/mruby-marshal/src/marshal.cpp:252
#5 0x00000000004bf7b7 in (anonymous namespace)::marshal_dump (M=0x2a7f3c0) at /home/dvl/motri/mruby/build/mrbgems/mruby-marshal/src/marshal.cpp:678
#6 0x000000000046ddc8 in mrb_vm_exec (mrb=0x2a7f3c0, proc=0x2e18f10, pc=0x2e432d0) at /home/dvl/motri/mruby/src/vm.c:1325
#7 0x000000000046c01a in mrb_vm_run (mrb=0x2a7f3c0, proc=0x2e18f10, self=..., stack_keep=5) at /home/dvl/motri/mruby/src/vm.c:861
#8 0x000000000047489b in mrb_top_run (mrb=0x2a7f3c0, proc=0x2e18f10, self=..., stack_keep=0) at /home/dvl/motri/mruby/src/vm.c:2748
#9 0x0000000000485da0 in mrb_load_exec (mrb=0x2a7f3c0, p=0x2e365e0, c=0x2e36400) at /home/dvl/motri/mruby/mrbgems/mruby-compiler/core/parse.y:5780
#10 0x0000000000485e16 in mrb_load_file_cxt (mrb=0x2a7f3c0, f=0x2e361b0, c=0x2e36400) at /home/dvl/motri/mruby/mrbgems/mruby-compiler/core/parse.y:5789
#11 0x0000000000446788 in main (argc=2, argv=0x7ffdd62c5398) at /home/dvl/motri/mruby/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c:227