brainfuck vm example does not compile

[ba0f3]

I tried and it works with 1.2 but not current stable version 1.4 or dev

/opt/workspaces/photon-jit/photon_jit/x86_64/x86_64_op_generator.nim(250, 18) Error: 'a' is of type <var Assembler[x86_64_base.X86_64]> which cannot be captured as it would violate memory safety, declared here: /opt/workspaces
/photon-jit/photon_jit/x86_64/x86_64_op_generator.nim(244, 18); using '-d:nimWorkaround14447' helps in some cases

Nim Compiler Version 1.4.0 [Linux: amd64]
Compiled at 2020-10-18
Copyright (c) 2006-2020 by Andreas Rumpf

git hash: bdcd87afca238a0a7b2c70971827cf9172817b12
active boot switches: -d:release