Disabling old-style registration results in error 500

When I want to bootstrap a new node after disabling old-style registration, I get a 500:

knife bootstrap <new-node> -r "role[base]" 
Creating new client for 
ERROR: Server returned error 500 for https://*******.dock42.com/clients, retrying 1/5 in 4s
ERROR: Server returned error 500 for https://*******.dock42.com/clients, retrying 2/5 in 7s
ERROR: Server returned error 500 for https://*******.dock42.com/clients, retrying 3/5 in 16s

==> /var/log/opscode/opscode-erchef/erchef.log <==
2015-04-06 12:51:14.716 [error] {<<"method=POST; path=/clients; status=500; ">>,{error,badarg,[{re,run,[null,{re_pattern,0,0,<<69,82,67,80,91,0,0,0,16,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,48,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,93,0,39,25,77,0,0,0,0,0,96,255,3,254,255,255,135,254,255,255,7,0,0,0,0,0,4,32,4,255,255,127,255,255,255,127,255,71,26,84,0,39,0>>}],[]},{chef_client,valid_name,1,[{file,"src/chef_client.erl"},{line,293}]},{chef_client,parse_binary_json,3,[{file,"src/chef_client.erl"},{line,232}]},{chef_wm_clients,validate_request,3,[{file,"src/chef_wm_clients.erl"},{line,89}]},{oc_chef_wm_base,malformed_request,2,[{file,"src/oc_chef_wm_base.erl"},{line,753}]},{webmachine_resource,resource_call,3,[{file,"src/webmachine_resource.erl"},{line,186}]},{webmachine_resource,do,3,[{file,"src/webmachine_resource.erl"},{line,142}]},{webmachine_decision_core,resource_call,1,[{file,"src/webmachine_decision_core.erl"},{line,48}]}]}}

==> /var/log/opscode/opscode-erchef/crash.log <==
2015-04-06 12:51:14 =ERROR REPORT====
{<<"method=POST; path=/clients; status=500; ">>,{error,badarg,[{re,run,[null,{re_pattern,0,0,<<69,82,67,80,91,0,0,0,16,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,48,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,93,0,39,25,77,0,0,0,0,0,96,255,3,254,255,255,135,254,255,255,7,0,0,0,0,0,4,32,4,255,255,127,255,255,255,127,255,71,26,84,0,39,0>>}],[]},{chef_client,valid_name,1,[{file,"src/chef_client.erl"},{line,293}]},{chef_client,parse_binary_json,3,[{file,"src/chef_client.erl"},{line,232}]},{chef_wm_clients,validate_request,3,[{file,"src/chef_wm_clients.erl"},{line,89}]},{oc_chef_wm_base,malformed_request,2,[{file,"src/oc_chef_wm_base.erl"},{line,753}]},{webmachine_resource,resource_call,3,[{file,"src/webmachine_resource.erl"},{line,186}]},{webmachine_resource,do,3,[{file,"src/webmachine_resource.erl"},{line,142}]},{webmachine_decision_core,resource_call,1,[{file,"src/webmachine_decision_core.erl"},{line,48}]}]}}

==> /var/log/opscode/opscode-erchef/current <==
2015-04-06_10:51:14.72501 [error] {<<"method=POST; path=/clients; status=500; ">>,{error,badarg,[{re,run,[null,{re_pattern,0,0,<<69,82,67,80,91,0,0,0,16,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,48,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,93,0,39,25,77,0,0,0,0,0,96,255,3,254,255,255,135,254,255,255,7,0,0,0,0,0,4,32,4,255,255,127,255,255,255,127,255,71,26,84,0,39,0>>}],[]},{chef_client,valid_name,1,[{file,"src/chef_client.erl"},{line,293}]},{chef_client,parse_binary_json,3,[{file,"src/chef_client.erl"},{line,232}]},{chef_wm_clients,validate_request,3,[{file,"src/chef_wm_clients.erl"},{line,89}]},{oc_chef_wm_base,malformed_request,2,[{file,"src/oc_chef_wm_base.erl"},{line,753}]},{webmachine_resource,resource_call,3,[{file,"src/webmachine_resource.erl"},{line,186}]},{webmachine_resource,do,3,[{file,"src/webmachine_resource.erl"},{line,142}]},{webmachine_decision_core,resource_call,1,[{file,"src/webmachine_decision_core.erl"},{line,48}]}]}}

==> /var/log/opscode/nginx/access.log <==
******* - - [06/Apr/2015:12:51:14 +0200]  "POST /clients HTTP/1.1" 500 "0.027" 36 "-" "Chef Knife/12.2.1 (ruby-2.1.5-p273; ohai-8.2.0; x86_64-darwin14.0; +http://opscode.com)" "127.0.0.1:8000" "500" "0.007" "12.2.1" "algorithm=sha1;version=1.0;" "vogl" "2015-04-06T10:46:39Z" "X9qKxCeT7YDiMqp3ajKF+ajFw6s=" 1548

Start with src/chef_client.erl at valid_name/1 and parse_binary_json/3, then follow validation through src/chef_wm_clients.erl. Reproduce the POST /clients request after disabling old-style registration and use the erchef and nginx logs to confirm the failure is handled without returning HTTP 500.